________ the book if you are free, and you will learn a lot about how to study English.

A．Read

B．Having read

C．To read

D．Reading

住宅内插座，低于( )时，应采用安全型插座且配电回路设有漏电电流动作保护装置时，其安装高度可不受限制。

A．0.3m

B．1.5m

C．1.8m

D．2.3m