Correct answer: C). They allow the deep ocean to be explored.
Due to the development of submarine technology like a submersible, the deep sea exploration is possible. Previously it was hard to believe that in the deep sea life exist, but due to the development of submersible, it showed that it is possible. It enabled the scientist to advance their studies in the field of deep sea surveying, marine ecology etc.
Hence, the correct answer would be option C
