Answer:
[tex]\boxed {\boxed {\sf A. \ Change \ in \ state \ of \ matter}}[/tex]
Explanation:
A physical change occurs when only the physical properties change. They are generally reversible and no new substances are formed.
However, in a chemical change, the chemical structures and properties change, plus new substances are formed.
Let's analyze each answer choice.
1. Change in state of matter
The state of matter is a physical property, so this is a physical change.
2. Precipitate was formed
A precipitate is a solid formed in a liquid solution. This is a new substance and a chemical change.
3. Unexpected change in odor.
A change in odor is a sign of chemical change.
4. Formation of bubbles
Bubbles signify the formation of gas or a new substance.
So, the best answer choice is A. change in state of matter
