问题
单项选择题
The contract is signed by the buyerand the seller in two original copies（）party holds one copy。
A．both
B．each
C．two
D．either
答案
参考答案：B
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The contract is signed by the buyerand the seller in two original copies（）party holds one copy。
A．both
B．each
C．two
D．either
参考答案：B
为等价无穷小，则a=().