Which statement best explains why invertebrates often have outer skeletons but vertebrates do not?
The outer skeleton provides protection, since invertebrates do not have backbones.
The outer skeleton surrounds the spinal cord, since invertebrates do not have backbones.
The outer skeleton helps invertebrates maintain homeostasis, since they lack spinal cords.
The outer skeleton helps invertebrates maintain homeostasis, since they lack membrane-bound organelles.

The outer skeleton provides protection, since invertebrates do not have backbones

Explanation:

The spinal cord (backbone) contributes to the body's protection. Using the human body as a case study, the backbone protects the body as it supports all skeletal structure of the body. But to cover up for that in most invertebrates, they need an outer steleton for protection from damage due to movement and dangerous foreign chemicals.

the answer would be d

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.