A central bank can control the money of stock by:Ⅰ. establishing reserve requirements for depository institutions Ⅱ. buying and selling government securities in the open market Ⅲ. setting the interest rate at which it will loan funds to commercial banks and other depository institutions Which of the following is FALSE（）

A. Ⅰ only.

B. Ⅱ only.

C. none.

我国长江中上游防护林的主要作用是(　　)

A．吸烟降尘、防风固沙

B．净化空气、美化环境

C．涵养水源、保持水土

D．为野生动物提供栖息地