He is ______ is known as a hacker ---- he likes to show off on the Internet and attack websites.

A．who

B．what

C．that

D．which

不能用于鉴别二氧化碳和氧气的是

A．燃着的木条

B．颜色、气味

C．紫色石蕊试液

D．澄清石灰水