有一读者问： 有这样一道改错题：
(1)Mercury's velocity is so (A: much) greater than the (B: Earth's) that it completes more than four revolutions around the sun in the time (C: that) takes the Earth to complete (D: one).
答案是C错，为什么？
“It takes（需要）...to...”是一常用句型，所以这里不可用that，应用it。这种句型中的takes之后常接“名词+时间词”，上述句中的“the time it takes the Earth to complete one”即是如此。再如：
(2)It took her three hours to mend her bicycle.
(3)It took us all day to drive home.
(4)How long will it take the letter to reach London?
这种句型还有不少别的用法，如：
(5)It only takes ten minutes to get there.
(6)It takes two to make a quarrel. 一个巴掌拍不响。
(7)It takes stamina to run a marathon.
(8)It would take a strong man to lift that weight.
