(a) Both Assertion and Reason are true and Reason is a correct explanation of Assertion.
3+7=9 is obviously false and this is a statement.
Using the laws of natural numbers, this statement can be proved to be false.
Thus, 3+7=9 is a statement since this statement is false, and it is not true at the same time.
Thus, Reason and Assertion are true, and the Reason is a correct explanation of the Assertion.