Sun Tiantian , _______ , is a professional tennis player from Zhengzhou.

A．a eighteen years old girl

B．an eighteen-year-old girl

C．an eighteen years old girl

D．a eighteen-year-old girl

下列现象或事实可用同一原理解释的是

A氯化铵晶体和碘晶体加热都产生气体

B．明矾和液氯都可用于处理生活用水

C．漂白粉和过氧化钠都可用于漂白有色织

D．常温下，铁和铜分别放在浓硫酸中都无明显现象