当你看到窨井盖缺失时，首先想到会发生什么（）？
A.人员坠落
B.交通事故
C.中毒窒息
D.环境污染
参考答案：A
As we are ______ the market for Table Cloth, we should be glad if you would send us your best quotation.
A．in
B．on
C．entering
D．at
电视节目的图象信号电视伴音分别采用哪种调制方式？
