招标人与中标人签订合同后（）个工作日内，应当向未中标的投标人退还投标保证金。
A.7
B.10
C.5
D.15
参考答案：C
My uncle _____________ well in _____________, ten years ago.[ ]
A. does; swimming
B. did; swimming
C. did; swim
456÷8的商是[ ]
A.55
B.56
C.57
D.58
