一个企业制订出HSE方针后，是永远不变的。
参考答案：错
There are two rooms on the first floor, _____ is used as a guest room .
A．a smaller of which
B．a smaller of them
C．of which the smaller
D．the smaller of them
理论上每个PON口可以支持（）个ONU。
A、32
B、16
C、64
D、8
