淋菌经______、______或______感染。

--- Would you like to go hiking with us for summer vacation?

--- Yes, I’d love to. _____ my parents have decided to take me to visit my grandmother.

A．Because

B．But

C．As

D．And

1970年，著名经济学家乔治·阿克尔罗夫发表了《柠檬市场：质量不确定和市场机制》的论文，开创了逆向选择理论的先河。( )

筒仓内起拱如何处理？

XY一3型钻机是用于（）孔岩心钻探的机型。

A.深

B.中探

C.浅