位于釉质牙本质交界处的许多小弧形凹线（）。

A.釉丛

B.釉梭

C.釉板

D.釉质牙本质界

E.釉质的生长线

It seems to some experts that 56．com, youku．com and tudou．com _____ 90% of the video market in this area．

A．make up

B．put up

C．set up

D．pick up