Explanation:

- Option 1: Amindivi Islands: These are part of the Lakshadweep group in the Arabian Sea, unrelated to the Andaman Islands.

- Option 2: Duncan Passage: It is the waterway separating Little Andaman from South Andaman in India. It is the correct geographical feature for this separation.

- Option 3: Reunion Hotspot: It is a volcanic hotspot in the Indian Ocean, unrelated to geographical separations in the Andaman Islands.

- Option 4: Minicoy Island: This island is part of Lakshadweep and is located in the Arabian Sea, not near the Andaman Islands.