The sulfur and nitrogen compounds in smog combine with water to form Acid Rain. Acid rain is harmful to the environment and infrastructure because of its aidic components.
The phases of the moon are created by the earth passing in front of the sun between the sun and the moon.
The correct answer is A.
Hunger, chemical imbalance, and blood levels are all internal issues. Cat dander on the other hand is not something the body creates or and is something in the environment.
Thus, your answer is A.
