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问题 单项选择题

焊接中碳钢时，尽可能采用（）低氢焊条

A.碱性

B.酸性

C.中性

答案

参考答案：A

选择题
设定义在实数集上函数f（x）满足：f（x+1）+f（-x-1）=0，f（x+2）=f（-x），且当0≤x≤1时，f（x）=3x-1，则有（　　）
A．f(
7
3
)＜f(-
3
2
)＜f(
9
4
)		B．f(
9
4
)＜f(-
3
2
)＜f(
7
3
)
C．f(
7
3
)＜f(
9
4
)＜f(-
3
2
)		D．f(-
3
2
)＜f(
7
3
)＜f(
9
4
)
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选择题

The first prize winner _______, John was so disappointed that he felt unwilling to know the rest of the results.

A．announcing

B．announced

C．having announced

D．had been announced
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