M800各种保护类型的保护倒换时间均满足ITU-T的小于（）的要求。
A.100ms
B.50ms
C.20ms
D.10ms
参考答案：B
He ____ to lend me his bike but I refused, for I didn’t want to trouble him.
A．failed
B．offered
C．considered
D．insisted
按突起路标的逆反射性能，分为A、B两类，具备逆反射特性的突起路标为A类突起路标，不具备逆反射特性的突起路标为B类突起路标。 ( )
