What is made up of dead skin cells

Cuticle
Cortex
Medulla

Hair is made up of columns of dead keratinised cells. The hair has three layers: A central medulla, or core (not seen in fine hairs), surrounded by a keratinised cortex, and the outer third layer, which is highly keratinised and forms the thin hard cuticle on the outside of the hair.

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.

nucleus

would be most reasonable answer tbh