题目内容：

改被动 you may write this letter in pencil someone must take care of the children when we go out
we must pay attention to such problems
we must finish the work by six o'clock this afternoon

优质解答

such problems must be paid attention to by us.the work must be finished by us by six o'clock this afternoonyou may write this letter in pencil this letter may be written by you in pencil.someone must ...