（）既可以规避风险，又可以相对降低成本。
A.保护性策略
B.备兑开仓策略
C.双限策略
D.买入认沽期权策略
参考答案：C
- _____ will you play basketball with me?
- In about 20 minutes after finishing my homework.[ ]
A. How soon
B. How long
C. How often
D. How far
