【单选题】You need skills _____________ a mountain bike. [ ]
【单选题】In the competitive market for balloon rides, marginal social cost equals marginal social benefit when 3,000 balloon rides a day are taken and the price of a ride is $130. Which of the following statem...
A.
There is a free-rider problem.
B.
Too many rides are available.
C.
Too few rides are available and the price of a balloon ride is too high.
D.
The efficient quantity of balloon rides is 3,000 a day.
【多选题】这则新闻主体部分主要讲述了哪些内容 ?
A.
1958 年毛泽东发出 “ 我们也要搞人造卫星 ” 的批示
C.
1970 年 4 月 24 日,中国成功地将自己的第一颗人造地球卫星送上了太空
D.
1992 年中共中央做出实施中国载人航天工程的战略决策
【单选题】Do you usually ____________ to school? [ ]
【单选题】--- I’d like a mountain bike which ____ well? --- Will this one _____?