The Andaman group and Nicobar group of islands are separated from each other by the Ten Degree Channel. The Ten Degree Channel is a narrow stretch of water located in the Bay of Bengal. It gets its name from its approximate latitude, which is around 10 degrees north of the equator. The Great Channel mentioned in option 2 is not the correct answer, as there is no such geographical feature separating these island groups. The Bay of Bengal, mentioned in option 3, is a large body of water to the east of India, but it does not separate the Andaman and Nicobar islands. Similarly, the Andaman Sea, mentioned in option 4, does not act as a barrier between these island groups.