山地铁塔地面组装时，山坡上的塔片垫物应（），且应有防止构件滑动的措施。
参考答案：稳固
Traditionally, college students hold a graduation party to encourage themselves before they _____ on their life journey.
A．give up
B．settle down
C．get through
D．set off
N型半导体主要靠（）导电的。
