_____ is known to all is that effective measures should be taken to deal with the problem of the over-exploiting of our resources.

A．What

B．It

C．As

D．Which

宽松的货币政策是指中央银行在公开市场上购买( )，降低准备金率，降低贴现率。

A．政府债券

B．私人债券

C．企业债券

D．贴息债券