（）是把被镀的金属材料浸入熔化的镀层金属液中，经过一段时间取出，使金属表面沾上一层镀层金属。
A.热镀
B.渗镀
C.电镀
D.喷镀
参考答案：B
22. The computer programs are a puzzle to me. The more I think of them, the more questions I think of .
A．ask
B．asked
C．being asked
D．to ask
合同在什么时间成立？
