用be 动词的适当形式完成句子。

1.There ____ ( be) a great number of books in the shelves.

2. The number of guests invited ____ (be) 50,  but a number of them ____ (be)absent for the heavy rain.

3. Quantities of water ____ (be) polluted now.

4. A great deal of oil ____ (be)poured into the sea and did great harm to creatures in the water.

5.  Many a  famous  writer ____  ( be) an  alumnus ( 撰搞人) of a local newspaper.

普通车床床身浇注时，导轨面应该（）

A.朝上

B.朝下

C.朝左侧

D.朝右侧