Task: Question Generation
Input (English): Miami's heavy-rail rapid transit system, Metrorail, is an elevated system comprising two lines and 23 stations on a 24.4-mile (39.3 km)-long line. Metrorail connects the urban western suburbs of Hialeah, Medley, and inner-city Miami with suburban The Roads, Coconut Grove, Coral Gables, South Miami and urban Kendall via the central business districts of Miami International Airport, the Civic Center, and Downtown. A free, elevated people mover, Metromover, operates 21 stations on three different lines in greater Downtown Miami, with a station at roughly every two blocks of Downtown and Brickell. Several expansion projects are being funded by a transit development sales tax surcharge throughout Miami-Dade County.
Output (English): How many lines does Metromover have?