May 12, 2008 , a terrible earthquake happened in Wenchuan . Lots of buildings __________ , and many students lost their lives .                           

A．fell down

B．got down

C．sat down

D．put down

一定数量的石灰和粉煤灰或石灰和煤渣与其他集料相配合，加入适量的水，经拌和、压实及养护后得到的混合料，当其抗压强度符合规定要求时，称为( )。

A．石灰工业废渣稳定土
B．水泥稳定土
C．石灰稳定土
D．水泥工业废渣稳定土