单项选择题
The students didn’t manage to work out the problem () their teacher had explained how.
A. when B. until C. unless D. as
单项选择题 They showed us around the factory ()is equipped with modern machines.
单项选择题 Some people think () about their rights than about their duties.
单项选择题 "What are you going to study next year" "I don’t know, but it’s time () something."
