This is an Assertion-Reason question, so it must be resolved by independently testing the truth of the Assertion, independently testing the truth of the Reason, and then separately checking whether the Reason actually explains the Assertion, since a wrong combination of any of these three checks can eliminate an option even where individual statements look plausible.
Testing truth and explanatory connection together shows that both statements are true and are correctly linked to each other.
Hence, the correct answer is both (A) and (R) are true, and (R) is the correct explanation of (A).