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

tsd is temerature dependent sex determination.

tsd: it is a type of environmental sex determination in which the temperature experienced during embryonic/ larval development (ambient temperature for development) determine the sex of the offspring.

crocodile displays the tsd where the ambient temperature of the developing egg determines the individual's sex. for example in the american alligator's eggs, incubation at 33 ºc produces mostly males, while incubation at 30 ºc produces mostly females. so if the american alligator's egg will get the ambient temperature (33 degree celcius)during embryonic development from egg, the offspring will be male and same for the female sex determination.

there's the proffessional site that will you.