My first _______ of Mr Zhang was that he was a serious person , but in fact, he’s very friendly.
--How long are you staying? ---I don't know. ____.
Fruit juices can be harmful ___ children’s teeth.
--Have you fed the dog?---No, but ____.
The farmers were more anxious for rain than the people in the city because they had more ______.
As is often pointed out, knowledge is a two-edged weapon which can be used ______ for good or evil.