Answer: Option (A) is the correct answer.
Step-by-step explanation:
Chemical changes are defined as the change which tend to show difference in chemical composition of a substance.
For example, toxicity, reactivity, combustion etc are all chemical properties.
So, in the given situation formation of bubbles shows that a gas has been formed which is a chemical change.
A chemical change will always lead to the formation of a new compound and this change is irreversible in nature by any physical means.
On the other hand, a change which is unable to bring any difference in chemical composition of a substance is known as a physical change.
For example, change in shape, size, mass, volume etc are all physical properties.
Thus, we can conclude that a gas is formed is an indication that a chemical change has occurred.