某次地震期间，为了紧急安置60名地震灾民，需要搭建可容纳6人或4人的帐篷，若所搭建的帐篷恰好（即不多不少）能容纳这60名灾民，则不同的搭建方案有     种．

In the time of social reform,people’s state of mind tends to         with the rapid changes of society.

A．keep pace

B．keep touch

C．go on

D．make progress