<u>My work:</u> Acid rain is a big pollution. Acid rain is caused by smoke in a rain cloud do to pollution from smock factories.This make A correct, because even if though Sewage treatment plants clean pollution they produce pollution from there plants.
A physical change requires a change in a physical property but the material does not change its uniqueness. Baking powder and cornstarch are only comparable in a way that they are both are white powders (same color) but they have separate and independent purposes in cooking and taste quite different.
