The correct answer is option 1, an aircraft carrier. INS Vikramaditya is an aircraft carrier of the Indian Navy. It is a modified and refurbished version of the Russian Navy`s Admiral Gorshkov-class aircraft carrier. The ship was commissioned into the Indian Navy in 2013, after undergoing extensive modernization and refurbishment works in Russia.

An aircraft carrier is a large warship that serves as a floating airbase for carrying and deploying fighter aircraft, helicopters, and other aircraft for combat operations. INS Vikramaditya can carry a variety of aircraft, including fixed-wing planes and helicopters, which can be used for various military missions, such as aerial reconnaissance, surveillance, anti-submarine warfare, and air defense.

It is important to note that the other options provided in the question are incorrect. INS Vikramaditya is not a nuclear submarine, a memorial for sailors, or a naval hospital. Rather, it is a powerful aircraft carrier that significantly enhances the Indian Navy`s capabilities for defense and maritime operations.