The new Hukou(户口) policy, according to some experts, ______ to attract more high-end talents to contribute to Shanghai’s development.

A．serves

B．serving

C．to serve

D．is served

下面属于极保护的有（）。

A.直流谐波保护

B.接地极线开路保护

C.中性母线差动保护

D.直流线路保护