用段保护需要APS协议实现，APS协议在复用段开销的（）字节中传送。
A.K1、K2
B.B1\B2
C.S1
D.K2
参考答案：A
How______the world be different in the future? [ ]
A. has
B. does
C. will
D. did
青光眼
