化工污染来源是（）。
A、燃烧的气体
B、反应产品
C、反应完全
D、反应副产品
参考答案：D
No one can imagine the difficulty he had _______ his son to get rid of the habit of playing computer games.
A．persuading
B．to persuade
C．persuaded
D．persuade
什么是光隔离器？
