—Did any signs come up before the earthquake?

—Yes. Unusual things             all those days. For example, a number of animals got out their homes.

A．happening

B．were happening

C．has happened

D．had happened

行政机关对于申请人提出的行政许可申请材料，若发现存在可以当场更正的错误，应当( )。

A．退回申请材料

B．允许申请人当场更正

C．替申请人更正

D．不予受理