—I saw a UFO                on the square in my dream.

—Really? It must be a fantastic dream. [ ]

A. to land

B. land

C. landed

D. lands

按病变进展情况分为

A．浅龋、中度龋、深龋
B．窝沟龋、根面龋
C．胎面龋、继发龋
D．急性龋、慢性龋
E．静止龋、邻面龋