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).
1) when litmus paper is dipped into a acid solution, the litmus paper turns red.
<span>2) acid reacts with metals to produce hydrogen gas </span>
<span>3) the equation of an acidic substance begins with the letter 'H' such as HCl </span>
Troposphere has most of our clouds temperature etc