Poikilothermic animals are those which have the inability to regulate the core body temperature (as by sweating to cool off or by putting on clothes to warm up). These include fishes, reptiles.
Amniota is a group of limbed vertebrates that includes all living reptiles (class Reptilia), birds (class Aves), mammals (class Mammalia), and their extinct relatives. Amniotes are truly terrestrial
So, the correct answer is option A.