有一读者问：有一道选择题：
(1)Records are very_________learning English.
A. use for B. useful to C. useful for D. uses for
答案是C，可为什么不用B呢？
请记住 useful 与动名词之间常用 for, 再如：
(2)It is useful for travelling.
(3)Those old dusters will come in useful for polishing the car.
(4)A low-power microscope will be found useful for examining material such as the larger insect larvae.
顺便提一下，如表“在……方面”，亦可用 in, 如上述句（1）即可改作：
(5)It is useful in travelling.
再如：
(6)The book is useful in recording the details of several rare editions.
如指“对人而言”，则可用to,
(7)It will be most useful to me. （强调“我主观认为有用”）
但下面一句中又须用 for：
(8)It is a useful book for students. （for 在此强调“说话人客观上认为对学生有用”）
