Your desk is crowded with too many unnecessary things,including used papers and books.

You'd better __________ some of them.[ ]

A．remain  

B．resist

C．remove  

D．renew

强度高、透气性好，铸件质量容易得到保证的砂型是（）。

A.湿砂型

B.干砂型

C.表面烘干型

D.金属型