Many social workers went to Ya’an to help       clean water and food to local people to reduce their pain from the earthquake.

A．put out

B．come out

C．work out

D．give out

下列关于实验现象描述错误的是  [ ]

A、硫在氧气中燃烧发出蓝紫色的火焰

B、铁在氧气中燃烧时，火星四射，生成四氧化三铁

C、镁在空气中燃烧发出耀眼的白光

D、胆矾溶液中加入氢氧化钠溶液后产生蓝色沉淀