A super metropolitan region extending as union of conurbations is known as:

Megalopolis

The correct answer is Option (4) → Megalopolis

Megalopolis: This Greek word meaning “great city”, was popularised by Jean Gottman (1957) and signifies ‘super- metropolitan’ region extending, as union of conurbations. The urban landscape stretching from Boston in the north to south of Washington in U.S.A. is the best known example of a megalopolis.