关于光纤通信，下列说法正确的是 [ ]

A．光在光导纤维中经多次反射从一端传到另一端

B．光在光导纤维中始终沿直线传播

C．光导纤维是一种很细很细的金属丝

D．光信号在光导纤维中以声音的速度传播

.If you don’t know how to use an English word, the easiest way is to _____ a dictionary.

A．turn over

B．look up

C．examine

D．consult