D. Enzymes and antibodies
The example that does not exhibit sexual selection is:
D. male elephant seals fighting over territory and potential female mates
The competition for territory is also one that helps the elephant seals survive. This is because a seal with a larger territory is likely to have access to a greater amount of resources, ensuring its survival.
I believe the answer would be "Top Predators"
It is called Fluid Mosaic Model. It describes the structure of the plasma membrane as a mosaic component. The structures such as phospholipids, protein, carbohydrates and cholesterol gives the fluid like character of the plasma membrane.