I think it is c but I’m not 100% sure so wait for someone else to answer too maybe ?
Answer : Option C) vestigial structures.
Explanation : In the example of whales which is displaying the remnants of the pelvis and femur bones it seems to be the example of vestigial structures.
As vestigial structures are those anatomical feature which no longer seems to have a purpose in the current form of an organism of the given species.
Answer:
Myocardium
The Heart itself. The nearest organ is the blood supplied to the Myocardium (Heart muscle) by the Heart pumping oxygenated blood through the Coronary Arteries.