【29】A．forB．onC．byD．with

We usually think of pollution _____ a harmful waste substance.A、forB、asC、byD、about

A．InB．OnC．ByD．At

A．forB．ofC．byD．as

【C9】A．inB．onC．byD．to

【C10】A．overB．onC．byD．to

Tom helped her mother_____ the cooking.A.forB.onC.with