According to       WHO, health care plans are needed in all big cities to prevent     _________spread of AIDS. 

A．the ; the

B．the ;不填

C．a ; a

D．不填; the

个别牙出现窄而深的骨下袋并常伴牙周脓肿形成，应考虑

A．咬合创伤
B．单纯性牙周炎
C．青少年牙周炎
D．慢性龈炎
E．牙龈增生肥大