Which among the following is most highly intelligent mammal ?

The correct answer is Option (4) –Dolphin

Dolphins are well known to be one of the most intelligent species on the planet. They are highly capable of both learning and mimicry.

Dolphins in separate pods have been known to use mud to create traps for fish and collect sponges to use as protection as they search for food among coral.

These two examples demonstrate the ability of dolphins to manipulate their surroundings and employ tools to achieve an end.