工程造价咨询企业资质有效期为( )年。
A．2B．3C．4D．5
参考答案：C
—I’m very tired these days because of the senior high school entrance examination.
—Why not______music? It can make you ______.
A．listen to; relaxed
B．to listen to; relaxed
C．listen to; relax
D．to listen to; to relax
初次投入运行的系统和大修以后的系统，在运行（）时间内，很容易发生污物堵塞的现象。
A.3-5天
B.1-2周
C.1-2月
D.10-12天
