Final answer:
The evidence of a chemical reaction includes a color change, a change in temperature, and the production of a gas, indicating that all these changes are signs that a chemical reaction has occurred.
Step-by-step explanation:
Evidence of a chemical reaction includes several observable factors. These are known to be visual clues that a chemical reaction is likely taking place. Some of these indications include:
A color change occurring during the reaction.
The production of a gas which may involve formation of bubbles.
A change in temperature can be noted as heat is either absorbed or given off.
Formation of a solid product called precipitate.
A transfer of energy occurs as light or flame.
The correct answer to the student's question is D. All of these (a color change, a change in temperature, and the production of a gas) are evidence of a chemical reaction.