Task: Question Generation
Input (English): Passage: Charleston, North Charleston, Goose Creek, and Hanahan are home to branches of the United States military. During the Cold War, the Naval Base  became the third largest U.S. homeport, with 23,500 Navy and Marine personnel, and 13,200 civilians serving over 80 ships and submarines. In addition, the combined facilities of the Naval Base and Weapons Station created the largest U.S. submarine port.  The Charleston Naval Shipyard repaired frigates, destroyers, cruisers, submarine tenders, and submarines. Also during this period, the shipyard conducted refueling of nuclear submarines. The Weapons Station was the Atlantic Fleet's loadout base for all nuclear ballistic missile submarines. Two SSBN "Boomer" squadrons and a submarine tender were homeported at the Weapons Station, while one SSN attack squadron, Submarine Squadron 4, and a submarine tender were homeported at the Naval Base. At the 1996 closure of the station's Polaris Missile Facility Atlantic , over 2,500 nuclear warheads and their UGM-27 Polaris, UGM-73 Poseidon, and UGM-96 Trident I delivery missiles  were stored and maintained, guarded by a U.S. Marine Corps security force company. In 2010, the Air Force base  and Naval Weapons Station  merged to form Joint Base Charleston. Today, Joint Base Charleston, supporting 53 military commands and federal agencies, provides service to over 79,000 airmen, sailors, soldiers, Marines, coast guardsmen, Department of Defense civilians, dependents, and retirees.
Output (English): How many types of vessels did the Charleston Naval Shipyard repair?