What condition must be met for a battery to be rechargeable?
a. either its anode or its cathode must generate a gas as a result of the electrochemical reaction.
b. it must generate electricity via an acid-base reaction rather than via an oxidation-reduction reaction.
c. the battery must be open to the outside so that it can vent any internal pressure that builds up from gases within it.
d. the electrochemical reaction of the battery must be reversible.

D. The electrochemical reaction of the battery must be reversible.

Explanation:

The batteries are based on the production of an electric flux given by a redox reaction. This reaction is spontaneous and is thermodynamically favored.

Thus, when the reactants to the reaction are finished, the flow of current stops and ends. Therefore, when current is administered from another source, the reaction changes its direction and reagents that were previously consumed begin to occur. Therefore the condition for it to be rechargeable is that the reaction can go forward or backward, that is, it is reversible.

it would be a gas formation