选择填空。

— Morning, Mr. Wu!             do you usually go to work?

— By bus.[ ]

A. How much

B. What

C. How

D. When

死髓牙根尖部牙龈出现瘘管应考虑为

A．根尖囊肿

B．慢性牙髓炎

C．慢性根尖脓肿

D．慢性根尖肉芽肿

E．慢性牙周炎