6. White-collar workers across China are becoming____ concerned about the impact of the global financial crisis on their careers.

A．highly

B．strictly

C．hardly

D．increasingly

某一无色溶液具有下列性质：①使无色酚酞试液变红；②与CuSO₄溶液反应可产生蓝色沉淀；③与纯碱溶液反应产生白色沉淀．此溶液是（　　）

A．氢氧化钠溶液

B．澄清石灰水

C．氯化钙溶液

D．盐酸