-- I’m very tired these days because of studying for physics.

--Why not    music? It can make you    .

A．listen to; relaxing

B．to listen to; to relax

C．listening to; relaxed

D．listen to; relaxed

S320的交叉板能完成光路方向（）个STM1和支路方向（）个STM1之间的低速率支路单元的时隙全交叉.