Which of the following statements about different types of bonds is least likely correct（）

A. Municipal bonds are traded primarily on the New York Stock Exchange.

B. Tax-backed bonds are backed by the full faith and credit of the issuer’s entire taxing power.

C. Government-sponsored enterprises issue securities directly in the marketplace, but federally related institutions generally do not.

大量用户出现无法解析网站，可能原因为（）

A.DNS服务器异常

B.DNS系统上行电路拥塞

C.DNS系统遭受DDOS攻击

D.用户电脑故障