Question

what is a disadvantage of incineration? air pollution emissions are challenging. the ash produced is harmless. facilities are free to build. it produces a lot of electricity.

Explanation:

Incineration can release pollutants into the air, which is a significant drawback. The ash produced may not be harmless (contradicting the second option). Building incineration facilities is not free (contradicting the third option). Producing electricity is an advantage, not a disadvantage (contradicting the fourth option).

Answer:

Air pollution emissions are challenging.