用锤击焊缝法来减少焊接变形和应力时，对底层和表面焊道一般（），以免金属面冷作硬化。
A.用锤轻击
B.用锤重击
C.不锤击
参考答案：C
I like this 3G cellphone very much, but it costs almost _______that one.
A．four times as many as
B．as four times many as
C．four times as much as
D．as four times much as
牙周膜纤维的主要成分是（）
A.胶原纤维和Oxytalan纤维
B.胶原纤维和网状纤维
C.网状纤维和弹力纤维
D.Oxytalan纤维和弹力纤维
E.弹力纤维和胶原纤维
