这当然只是指全句主语表示事物或抽象概念时而言，全句主语如指人则是另一回事了。
2 across与through不同
有一读者问： 有这样一道选择题：
(1)The small river runs_________the forest quietly.
A. in B. across C. through D. on
应选B还是C? 有人说across指“横过”，through指“通过”，方向垂直。但词典中却有这样一例：
(2)The river flows from west to east through the city.
不知作何解释。
介词across的确常意指“横过”，一般强调从一边横向到另一边，遂即停止，如横过一条街、一条河等，实例如：
(3)He went across the street. （强调过街为止，至于过街后如何，那就是另外一回事了）
(4)There is a bridge across the river.
介词through的本义是“穿过”或“通过”，可意为直穿过，也可意为横穿过，也可意为斜穿过，穿过之后一般并不就此停止，上述句（2）即是一例。再如：
(5)We drove through the town.
(6)The rain poured through a hole in the roof.
由此可见，上述句（1）应选用through。
3 这里用 through 与用 across 有何不同？
有一读者问：有这样两句话：
(1)An Arab was walking alone through the desert ...
(2)It winds its way from west to east, across deserts, over mountains,through valleys ...
为什么在 desert(s)之前一个用 through，一个用 across?
through 和 across 皆可译作“穿过”或“越过”，用在 desert 之前。但 throught the desert 强调“穿过沙漠的范围”，across the desert 强调“横过沙漠的表面”。
4 这里应选什么介词？
问：有这样一道选择题：
The river's mouth is 220 miles wide, ocean-going ships can travel 1，000 miles_________the river.
A. along B. up C. down D. by
应选A还是应选C?
从上下文来看显然应选C， 以表远洋船只可“沿江而上”1，000英里。
5 为何用after而不用in?
有一读者问： 有这样三个句子：
(1)Wang Bing is leaving the USA after two years.
(2)Yang Pei is leaving Australia after two years.
(3)Peter and Bill are leaving China after three years.
这里为何不用in而用after?
这里既可用in亦可用after。但二者是有区别的。in two years可意为“两年之后”，亦可意为“两年之内”。而after two years则只有一个意思，即“两年之后”。
6 as for, as to, as far as...is concerned
有一读者问： as for, as to 和 as far as...is concerned 有何区别？可否通用？
这三种说法有时是可以通用的，且看下面三个句子：
(1)As for me, I am not satisfied.
(2)As to me, I am not satisfied.
(3)As far as I am concerned , I am not satisfied.
这三个句子中的 as for, as to 和as far as...be concerned有几个共同点：1.皆意谓“就……而论”；2.皆是一种补充性声明，用以引起人们的注意；3.皆用作状语，位于句首。然而，上述三种说法并不完全等同，它们是各有其特点的。现将它们各自的特点分别作一探讨。
让我们先谈 as for。这是一短语介词，其后须接名词或代词。它有以下几个特点：
1. 它一般皆位于句首，意谓“就……而论，至于”，如上述句（1）。它很少位于句中，我们只见到过一例如下：
(4)He inquired as for my health.
2. 它常用来表示新的前文未提到过的事物（但也有用以表示前文已提到过的事物的情况），如：
(5)I know not what course others may take, but as for me, give me liberty, or give me death. （摘自美国政治家 Patrick Henry 1775年所作的演说）
(6)Much pasture land is under water; and as for the grain, most of that has been ruined. （as for 常与 and 连用）
3. 它较 as to 更加具有强调的意味，而且可有轻蔑、消极、不甚重要等含义，如：
(7)I've invited Andy, Bob and Mark. As for Stephen, I don't care if I never see him again in my life.
(8)The main dish was palatable, but as for the soup and the dessert...! （as for 常与 but 连用）
(9)That's the answer. As for the cause, how do I know?
(10)As for the rest of my infancy, there being nothing in it remarkable, I shall pass it over in silence.
4. as for 有时可省去，如：
(11)Myself, I wouldn't take any notice of her. （myself 之前省去了 as for）
5. 有些人说它的使用频率要高于 as to。
as to 也是一个短语介词，其后须接名词或代词，它有以下几特点：
1. 它不但可位于句首，如上述句（2），而且可以位于句中。位于句首时意谓“就……而论，至于”，常用以表示前文已提到过的或是已被料到的事物（但也有表示前文未提到过的事物的情况），如：
(12)As to that, I haven't decided yet.
(13)As to Smith, it is impossible to guess what line he will take.
(14)As to the journey, we must decide about that later.
(15)As to your suggestion that I fly out to see you, I don't think this would be a good idea.
2. as to 位于句中时，则意谓“关于”。它可置于名（代）词之后，动词之后以及形容词之后，如：
(16)I have no opinion as to the result. （置于名词之后。置于代词之后的情况见上述句（2））
(17)I doubted as to the last article of this eulogy. （置于动词之后）
(18)The worst thing you can do to an author is to be silent as to his works. （置于形容词之后）
3. 位于句中的 as to 除可后接单词外，还常后接间接疑问句，尤常后接 whether 引导的从句，如：
(19)As to whether he will consent, it is still too early to say.
(20)They disagree as to how he works.
(21)As to why they gave up the project, I'm still wondering.
(22)I have often wondered as to where the money had vanished.
(23)I could not help speculating as to who was going to fill the vacancy.
(24)When in doubt as to which answer is right, follow the text.
(25)As to what he is going to do, I did not ask him.
4. 有人认为同位语前的 as to 是多余的，尤其是 whether 引导的同位语之前的 as to，如：
(26)There is some question as to whether the bill will pass.
但是也有人对此有不同的看法。他们说即使英语学者的著作也不免有用此所谓“多余的” as to 的情况。他们还说，除打电报时不用“多余的” as to 之外，其它场合用不用，还是听凭于个人的好恶吧。
5. 有人认为位于句中的 as to 常被滥用，应被别的介词所替代，如常可被 about ，concerning 所替代。例如上述句（16）与（18）中的 as to 即可代之以 about ，再如下面一句中的 as to 可以代之以 concerning：
(27)The manufacturer complains that everything as to the future is left to the whim of the Board of Trade.
6. 注意位于句中的 as to 有时并不意谓“关于”，如：
(28)He so behaved as to impress company favorably. （as to 在此与 so 连用，表示目的）
(29)Transport rates vary both as to distance and as to weight. （as to 在此意谓“与……成比例”）
最后谈谈 as far as ... be concerned。 它也是一种用作句子状语的说法，其义是“就……而论”。 as far as 之后须接名词或代词，例除上述句（3）除外，再如：
(30)As far as the weather is concerned , I do not think it matters.
(31)As far as money is concerned , I'm in the hands of the bank manager.
这一说法的特点有：
1. 它不但可位于句首，亦可位于句中，如：
(32)It does not matter how clean we are as far as breathing is concerned .
2. 亦可说 so far as...be concerned ，其义与 as far as...be concerned 完全一样，如：
(33)I didn't enjoy the movie, and so far as that is concerned , I never like horror movies.
3. 第一个 as 在口语中可省去，如：
(34)Far as he's concerned , every man wearing a badge is a fascist, a crook, or a hustler. （far 前省去 as）
4. 由于 as (so)far as...be concerned 这一说法比较笨重，因而在当代英语中往往省去了 be concerned ，只剩下 as (so)far as ，如：
(35)As far as temperament , the Abyssinian cat is a most affectionate and loving companion.
(36)As far as raising kids, he didn't have a clue.
(37)So far as the program, it will be developed later.
但这种缩略形式到现在似乎仍停留在非正式英语中，在书面语中仍是不省去 be concerned 的好。
5. 注意 as far as...be concerned 中的 be 有时与其前的名（代）词的数并不一致，尤其在口语中，如：
(38)As far as Adams and Mr. Cohn is concerned ...（应为 are）
(39)As far as the infiltration of the armed services were concerned ...（应为 was ，但这里的 were 也可能是由于受到了其前的复数名词 services 的影响之故）
6. as far as...be concerned 还有两种变体：一种是 as far as...goes （went 等），实例如：
(40)His account is true as far as it goes .
另一种变体是 as far as concerns...，由于较为少见，这里就恕不举例了。
7 apart from 与 aside from 有什么不同？
有一读者问： apart from 与 aside from 有何不同？
apart from 与 aside from 用作短语介词时，其意义与用法无甚不同，只是前者通用于英美两国，而后者则多用于美国而已。 apart from （或aside from）的用法值得我们注意的倒是：它除意谓“分开”“远离”外，有时还相当于“除开”(except for)，如：
(1)Apart from Patrick, the car is empty.
有时则相当于“撇开……不说”(besides)，如：
(2)Apart from the injury to his face and hands, he broke both legs.
8 at the end of the week 与 by the end of the week 之区别
有一读者问：有这样一道题：
I'll visit you_________the end of the week.
A. at B. by C. to D. till
答案为A，但我认为B也对，你看呢？
对。但二者意义上稍有不同。at the end of the week 意为“在周末”， by the end of the week 意指“临近，不迟于，最迟到”，有 before 的含义。
9 再谈 by the end of 与 at the end of 的区别
有一读者问：我想知道 by the end of 与 at the end of 的区别。有人说by the end of 常和完成时态连用，at the end of 则常和一般时态连用。但高中英语第一册却有这样一句话：
(1)At the end of six months he had learned enough to read articles and reports in Russian.
句中的 at the end of...之后却用了过去完成时 had learned, 请解答。
at the end of 后接时间词时，它与 by the end of （此短语常后接时间词）的区别不在于它们与什么时态连用，而在于 at 与 by的含义不同。at 表“在或正是在”， by 表“在……之前或不到”。所以你所引的句子中的 at the end of six months 的意思是“在6个月的末尾”， 如用 by the end of six months, 它的意思则是“在6个月之前或不到6个月”。
“by the end of + 时间词”确是常与完成时连用，但也可与其他一些时态连用，这里只举它可与过去一般时连用一例如下：
(2)The plants appeared wilted initially, but regained their vigor by the end of the 24-hour experimental period.
同样，“at the end of + 时间词”也不但可与一般时态等连用，它也可与完成时态连用，你所引用的上述句（1）即是一例。
你可能会问， by the end of 和 at the end of 既可与过去完成时连用，亦可与过去一般时连用，那么这两种时态又有什么不同呢？它们的不同之处在于过去完成时强调完成及其结果，过去一般时则只表述一个单纯的事实。
10 at night 与 in the night 有何不同？
有一读者问：at night 与 in the night 有何不同？
at night 表一时点。它首先多指傍晚或黄昏至午夜的时刻，如：
(1)He arrived at ten at night .
(2)I never read at night so as not to injure my eyes.
(3)He often calls to see me at night .
(4)Is that programme at ten o'clock in the morning or at ten o'clock at night ?
at night 常与 late 或 early 连用，如：
(5)I don't like going out alone late at night .
(6)I go to bed early at night .
at night 表傍晚时甚至可从下班后开始，如：
(7)Come home from work at night .
其次， at night 作为一时点亦可表整个夜间与at day或by day相对，如：
(8)Owls are most active at night .
(9)The moon shines at night .
(10)Nurses often have to work at night .
(11)Keep a light on at night .
at night 表整个夜间时常与 sleep 连用，如：
(12)I do not sleep well at night .
(13)Try these pills if you can't sleep at night .
再次， at night 常与 during the day 等相对比,如：
(14)He works in an office during the day and studies at night . （night 在此指前半夜）
(15)We work during the day and sleep at night . （night 在此整个夜间）
(16)They fought all day, and at night food and ammunition were brought up in carts. （night 在此亦表整个夜间）
in the night 表一时段，常有黑暗、危险的含义。它首先多指说话人说话时的前一夜间的某一或某些时刻，如：
(17)She woke in the night with a dreadful dream. （in the night 在此表前一夜间的某一时刻）
(18)I woke up twice in the night . （in the night 在此表前一夜间的某些时刻）
(19)In the night I've thought of things you said. （in the night 在此表前一夜间的某些时刻）
(20)She was describing a meteor which she had seen in the night . （in the night 在此亦表前一夜间的某一时刻）
其次，in the night 作为一时段亦可表整个夜间，如：
(21)There is no light in the night .
(22)This is an old English and American going-to-bed charm to keep children from being afraid in the night .
(23)Finally, to be quite sure that he would not be troubled by thieves in the night , he sat up in bed in the dark and said loudly,“Well, here I am in York, and without any money at all. ”
最后，应当指出，将 night 看作一时点或一时段，往往由说话人的心理因素而定。故而同一的意义，有的人用 at night 表达，有的人则用 in the night 表达，如：
(24)A fire occurred at night .
(25)A fire broke out in the night .
(26)Why does the bat come out only at night ?
(27)Bats come out in the night .
但下面两句中的 at night 与 in the night 的含义有所不同：
(28)He stole away at night , leaving a letter on my pillow. （at night 在此强调时间）
(29)The prisoner got away in the night . （in the night 在此有黑暗和危险的含义）
11 这里为什么分别用 at night 与 in the night？
有一读者问：初中英语新教材有这样几句话：
In the Northeast it will be fine. The temperature will stay above zero in the daytime, but at night it will fall below zero again. In the Northwest, there will be snow in the night.
请问 at night 与 in the night 有何不同？
在这里用 at night, 是由于与其前的 in the daytime 相对之故；用 in the night 则是为了强调时段的概念。
12 at one point ≠在这一点上
