问题
选择题
—The flowers are beautiful. How do you look after them?
—Well, this kind of flowers _________ every morning.
A. should water B. waters C. must be watered
答案
答案：C
题目分析：句意：--这些花是漂亮的。你是如何照顾他们的？--好，这种花每天都必须浇水。分析：考查被动语态的用法，花必须被浇水，情态动词的被动语态，构成：must be done(动词的过去分词)。故选C