Sharks and dolphins (aquatic mammals) have fairly similar morphology, the result of living in the same environment. However, many of these similarities are superficial. Which is the MOST DERIVED trait that sharks and dolphins share

shape- torpedo shaped , Fins- dorsal and side fins

Explanation:

Dolphin is a part of the Cetacean family, which also includes whales and porpoises while sharks are cartilaginous fishes of the class Chondrichthyes which means they have skeletons that are made of cartilage rather than bone. Shark and dolphin tends to look alike although the are not related but because they share the same habitat and have some similar body features such as Body shape, fin and tail they are mostly grouped together as the same.

natural selection favored a particular shape over other shapes for rapid movement through the seas and fin which made them a predator in the ocean this makes them look similar.

you didn't give any options but heres what i can tell you: an inference is likely to change based on additional observations. the latter is something that you have seen or sensed using your sensory organs while the former is like a conclusion out from what you have observed.