I will be surprised if you can get Calvin, who is very busy, ______these tickets for you.

A．buy

B．buying

C．buys

D．to buy

（）工艺主要用于中碳钢及低、中碳合金结构钢的锻件、铸件等。

A.扩散退火

B.完全退火

C.球化退火

D.去应力退火