请求信：…This decision was not taken lightly,and I do appreciate the king consideration you have shown to me .空气污染 ……Actually,people are showing a rel concern over the problem.For example, there is an increasingly loud voice from the public for firm action against pollution from automobiles.顺便问下，在背诵过程中，我老是记不清何时用for或from 、of等，请问老师如何才能准确得记住它们，谢谢！
