逆行性牙髓炎常见病因是()

A．深牙周袋

B．血运感染

C．牙周脓肿

D．根尖肉芽肿

E．创伤性合

. __________ you must do is to choose a scene __________ will best show your acting talent.

A．That; that

B．What; that

C．That; where

D．What; where