牙周炎时骨内袋的病理特点是（）。

A.牙槽骨发生垂直型吸收

B.牙槽骨发生水平型吸收

C.牙槽骨尚无吸收

D.牙周袋底位于牙槽嵴顶上方

E.牙槽骨嵴的高度明显较低

He said that light ______ much faster than sound. [ ]

A. has travelled

B. went

C. travels

D. travelled