I believe the answer to this is A.
The food chain always begins with a sun without it there would be no food chain... hope this helped!
Answer:
A. When two aqueous solutions are mixed, a precipitate is formed.
Explanation:
The precipitate (a solid substance that falls from the liquid) is the result of a chemical reaction taking place between the liquids.
The other three answer choices are indicative of physical changes (temperature change, phase change, color change).