What are research submersibles like alvin useful in studying?

The correct answer of the given question above would be sea floors or underwater. The research submersibles like Alvin are useful in studying sea floors or underwater. The Alvin submersible is owned and operated by Woods Hole Oceanographic Institution and was built in 1964. Hope this answer helps. 

These small submarines usually hold only a pilot and one scientist, but can record the ocean bottom through cameras. The small submarines usually hold only a pilot and one scientist, but can record the ocean bottom through cameras.

Ithink the answer you are looking for is (b).