Answer:
C. Release of Heat Energy
Reason:
-A chemical is any substance that has a definite composition
-A chemical reaction is the process by which one or more substances change to produce one or more different substances
-Matter is anything that has mass and volume
-Solids have fixed volume and shape
-Liquids have fixed volume, but not a fixed shape
-Gasses have neither fixed volume or shape
Evidences of Chemical Change:
1. Evolution of bubbles (gas) without a heat source
2. Formation of a precipitation (solids floating in a liquid)
3. Transfer of energy (it gets hot or cold)
4. Color change
In the part of the question, "They noticed that bubbles form, the test tube got hot, and the magnesium disappeared", it states nowhere about color change or change in odor.
