His uncle ______ for more than 9 years.[ ]

A. has come here        

B. has started to work

C. has lived there  

D. has left the university

王老汉在玻璃计量厂工作多年，长期接触和使用金属汞对量器进行校正。两年前，王老汉出现了全身乏力、失眠、牙齿松动等症状。没过多长时间，他脾气开始变得暴躁、易怒，家人以为他得了精神病。

汞在生产环境中主要以何种形态存在

A．烟尘
B．粉尘
C．蒸气
D．雾
E．气溶胶