What is an indication a chemical reaction has occurred? a.) formation of gas b.) boiling of a substance c.) melting of a substance d.) freezing of a substance

I believe the answer is A. Formation of gas. I found this answer by eliminating the rest because they only clearly show physical changes in the substance. So, I assumed the substance forming a gas would be due to a chemical change.

idk

explanation:

i need the pts ignore this answer

a  solution  is always transparent, light passes through with no scattering from solute particles which are molecule in size. the  solution  is homogeneous and does not settle out. a colloid is intermediate between asolution  and a  suspension. while asuspension  will separate out a colloid will not.