The answer is option “C”. A challenge is something that is hard.
Sentinel : sentire :: <span> sensuous : sonare.</span>
Answer:
For example, Killer whales are the largest member of this dolphin family, so they are both a whale and a dolphin at the same time. Because they belong to the Cetacean order,dolphins and whales share mammalian traits like warm blood, hair, and lung-based breathing.
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I think it’s the 3rd answer, I hope my answer is useful