Option 1: Gulf of Mannar - Palk Strait - Palk Bay

According to this option, the Gulf of Mannar is the northernmost position, followed by the Palk Strait, and finally the Palk Bay in the south. However, this is incorrect.

Option 2: Palk Strait - Gulf of Mannar - Palk Bay

This option suggests that the Palk Strait is the northernmost position, followed by the Gulf of Mannar, and finally the Palk Bay. However, this is also incorrect.

Option 3: Palk Strait - Palk Bay - Gulf of Mannar

According to this option, the correct sequence is the Palk Strait to the north, followed by the Palk Bay, and finally the Gulf of Mannar in the south. This is the correct answer.

Option 4: Palk Bay - Palk Strait - Gulf of Mannar

This option suggests that the Palk Bay is the northernmost position, followed by the Palk Strait, and finally the Gulf of Mannar. However, this is incorrect.

Therefore, the correct sequence of positions in the Bay of Bengal from North to South is Palk Strait - Palk Bay - Gulf of Mannar.