建筑施工工地，必须采用（）配电保护系统。
A．TN—S
B．TN—C—S
C．TN—C
D．TT
参考答案：A
Where were you at lunch time? I a seat for you in the dining hall.
A．saved.
B．was saving .
C．have saved.
D．had saved.
太阳从西边升起．______．（判断对错）
