单项选择题
The main cause of pollution is （）
A．the production of new industrial goods B．increased amounts of natural substance C．our ever-increasing population D．the release of artificial of natural substances into the environment
单项选择题 People can help solve the problem of pollution by （）
单项选择题 Many people see pollution as only part of （）
单项选择题 What happened when the man let go the rope（）
