配额与许可证这两种限制措施既可单独采用,也可以结合在一起使用,我国目前采用的是( )。
A.配额管理措施 B.许可证管理措施 C.配额许可证管理措施 D.以上都不对
参考答案:C
His parents thought he was working very hard in the room, _____in fact, he was chatting with his friends on the Internet.
A.when
B.where
C.which
D.while
黄河是世界含沙量最大的河流。()