Which of the following correctly describes amniotes?
a. all amniotes are exclusively carnivorous until adulthood.
b. adults store energy within the amnion until reproduction.
c. permeable, moist skin facilitates cutaneous respiration.
d. embryos develop within four extra-embryonic membranes.

The correct answer is D. Amniotes embryos develop within four extra-embryonic membranes.

Explanation:

Amniots are a clade of tetrapod vertebrates. They are characterized in that the embryo develops four envelopes: the chorion, the allantoids, the amnion and the yolk sac and creates an aqueous medium in which it can breathe and from which it can feed. This is an evolutionary adaptation that, unlike what happens with amphibians, allowed oviparous reproduction in a dry and terrestrial environment. Other adaptations are to have a dry and flaky skin due to an increase in the keratinization of the epidermis to avoid desiccation and dehydration; possess an exclusively pulmonary respiration and have an internal fertilization, with the abandonment of the larval phases and subsequent metamorphosis.