________ the teachers is about 300 in our school and it is becoming_____________.

A．The number of, more and more

B．The number of, bigger and bigger

C．A number of, more and more

D．A number of, bigger and bigger

水利工程施工起重作业时，下列哪些可以作为起吊重物的承力点（）。

A.脚手架

B.构筑物

C.设备的构件

D.现场未安装的管道