3.Since it was abnormal for mould to be in that lab dish, something must have gone wrong.

由于在实验室里的那个碟子里的霉菌是不正常的，所以一定是某些事情出错了。 must have done"一定做过......"，表示对过去情况的肯定推测。 He seems very nervous; something must_have_happened to him.

他看起来非常紧张，一定出什么事了。 　　

　　1．(教材P18)Both of these medicines have saved millions of people's lives and have proved beneficial to mankind since they were invented.

　　自这两种药被发明以来，它们已挽救了数百万人的性命，并已证实对人类有益。

　　beneficial adj. 有益的，有用的

　　(1)be beneficial to　　　　　　 对......有益

　　(2)benefit vi.& vt. 得益于；使受益

　　n. 利益，好处

　　benefit from/by 从......中受益

　　to one's benefit 对某人有益

　　be of benefit to (＝be beneficial to)

　　 对......有益

　　for the benefit of 为了......的利益

　　①Cycling is highly beneficial to health and environment.

　　骑自行车对健康和环境都非常有益。

　　②I really like to talk with him like this because I can benefit so much from/by it.

　　我真的喜欢和他像这样谈话，因为我可以从中受益很多。

　　③Proper exercise every day is of great benefit to our health.

　　每天做适量的运动对我们的健康很有好处。

　　④For_the_benefit_of the chemist, all the doctors and nurses went on a strike.

　　为了这名药剂师的利益，所有的医生和护士举行了罢工。

　　[名师点津]　of＋抽象名词＝该名词的形容词。有此种用法的词有：

　　①(be) of use＝useful

　　②(be) of help＝helpful

③(be) of value＝valuable