The organs which were useful in the ancestors but are not in use currently are not in use are referred to as vestigial structures, i.e., option B.
Vestigial is describes the structures in animal organs, tissues, or bones that may have been used by an ancestor but aren't anymore.
For example, snakes bear vestigial structures limbs that would have been when they walked on four legs.
In whales the pelvis and femur are vestigial organs.
Thus, the correct option is B.
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