— Do you know sound travels very fast?

— Yes. But light travels         sound.

A．as fast as

B．a little faster than

C．much faster than

D．slower than

急慢性白血病最主要的区别是（）

A.病程长短

B.病情严重程度

C.预后好坏

D.白血病细胞分化程度

E.计数白细胞的高低