— ______  is it from your house to the bus stop?

— About five minutes’ walk.

A．How far

B．How often

C．How soon

D．How long

牙周病活动期牙槽嵴吸收表现为

A．牙槽骨吸收边缘可见薄层致密骨形成

B．骨纹理增粗，骨硬板增厚

C．骨硬板不清晰，部分或全部消失

D．牙槽骨吸收边缘整齐、平滑

E．牙骨质增生，牙周膜间隙变窄甚至消失