促销主题有哪些？（）
A.开业促销活动
B.年庆促销活动
C.例行性促销活动
D.竞争性促销活动
参考答案：A, B, C, D
— Where are my trousers?
— _____ on the bed. [ ]
A. It's
B. They're
C. They were
D. It was
焊条有哪几部分组成？
