Answer:
Sexual reproduction.
Explanation:
Sexual type of reproduction used by the marine biologist in order to develop the new coral because variations in an organisms only be done with sexual reproduction. For producing new type of coral, the type of corals should be fused together in order to gain the desire characters in the organisms. So if the marine biologist want coral polyps with large stinging tentacles, sexual reproduction is the only way. From asexual reproduction, the offspring produce identical to parents so that's why we can't use asexual reproduction.