____, the boys were shouting and singing

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问题选择题

____, the boys were shouting and singing. [ ]

A. Happy and excited

B. Happily and excitedly

C. To be happy and excited

D. To be happily and excitedly

答案

答案：A

解答题

已知：A={x|x²+4x=0}，B={x|x²+2（a+1）x+a²-1=0}．

（1）若A∪B=B，求a的值；

（2）若A∩B=B，求a的值．

填空题

自由锻造的基本工序有______、______、冲孔、扩孔、弯曲、扭转、错移和切割等。