The correct answer is option 4: the President is bound to give his assent to a constitutional amendment bill. This means that once the bill has been passed by both houses of Parliament and is presented to the President, he does not have the power to reject or withhold his assent. The role of the President in this case is largely ceremonial, as he acts as a representative of the government and signs off on the bill to make it law. Options 1, 2, and 3 are incorrect because they imply that the President has the power to refuse or delay the passage of a constitutional amendment bill, which is not the case.