喷泉模型的优点是（）。
A. 各个阶段可以同步开发
B. 增大了投资的早期汇报
C. 减少了软件需求不明确带来的开发风险
D. 降低了在一个增量上的开支风险
We believe that an explosive device had been left inside a ___________.
A. contain
B. contained
C. contains
D. container
Store the peppercorns in an airtight ___________ and grind the pepper as you need it.
A. contained
B. contain
C. container
D. containers
There is always a strange ___________ of runners in the London Marathon.
A. collecting
B. collect
C. collection
D. collections
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