The plasma membrane is semipermeable because-

The plasma membrane is called a selectively permeable membrane as it permits the movement of only certain molecules in and out of the cells. ... It allows hydrophobic molecules and small polar molecules diffuse through the lipid layer, but does not allow ions and large polar molecules cannot diffuse through the membrane.

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a. by using fur or clothes to trap heat energy near the body

i believe the answer would be b. hope it : )