There are four underground lines in Beijing, and several lines are under _______(建设)
She opened the door quietly not to __________ (打扰)the sleeping boy.
One rainy night the policeman had a chance to __________ (遇到)a gang of smugglers.
It's very difficult to climb a s __________ cliff.
She stressed that point in __________ (尤其).
A red lamp is used as a danger __________(信号).