Unique feature of osmosis is that (1) energy is required
(2) it involves movement of solutes
(3) it occurs across membranes only
(4) it is seen only in animals

I believe the answer is (3)

Explanation:

"Osmosis is a special type of diffusion, namely the diffusion of water across a semipermeable membrane"

"Osmosis only occurs with a semipermeable membrane"

Khan and sciencedirect

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.