Internal gestation followed by live birth is an evolutionary development most likely driven by which of the following?

A. The need to give birth and reproduce on dry land where eggs could dry out

B. Environmental conditions caused eggs to over-absorb dangerous molecules from the environment

C. The inability of eggs to acquire nutrients to grow complex animals

D. The threat of predators to eat eggs

Answer: B is the correct answer

D. The threat of predators to eat eggs

Explanation:

The internal gestation followed by live birth was an adaptation developed by the mammals on land, and by some fish in the water, like the sharks. The mammals have been the most marking ones in this adaptation though. They too were producing eggs initially, but because they were living in an environment where there were numerous animals that preyed upon them, as well as their eggs, they had to be innovative. They developed internal gestation, where the embryo was developing inside the body of the female, and then it was born alive. This was providing extra safety, as the embryo was always with the mother, instead of being left alone and not guarded, thus an easy meal for the predators. The two types of internal gestation that the mammals developed are the placental and marsupial types, with the placental turning out to be more successful over time.