The Specific Relief Act lists out the grounds for rescission as a set of clauses, so the way to answer is simply to check whether both quoted scenarios appear among those clauses.
The correct answer is Both (a) and (b).
A helpful way to check whether an option quoting statutory language is correct is to compare it word for word against the actual text of the relevant provision on rescission in the Specific Relief Act.
Comparing the quoted language to the statute confirms that rescission may be sought under either scenario, so the answer is Both (a) and (b).