Vitamin b12 is important for the body to function. it keep nerve cells healthy, and it with the formation of red blood cells. when someone is vitamin b12 deficient, one of the reasons could be that the person’s is not the vitamin efficiently.

what is the question? is it 'what is one of the reasons that someone could be b12 deficent?

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.

a- all cells come from pre-existing cells