A major evolutionary change seen between fish circulatory systems and amphibian, bird and mammalian circulator

Question

circulatory systems is the presence of a

separate pulmonary circuit in fish

two chambered heart in amphibians, birds, and mammals

double loop pathway in amphibians, birds, and mammals

or

stronger atria in amphibians, birds, and mammals

Answer 1

Double loop pathway in amphibians, birds, and mammals.

Fish has a singular circulatory system, means the blood carrying oxygen from pulmonary circuit will be dumped into the same chamber as the blood carrying wastes and CO2 in the heart, because the heart has only one chamber.

amphibians has a 3 chamber heart, but still not a complete separated pulmonary circulation. However, it does have 2 loops at this stage. Of course birds and mammal also has this feature. So the distinction will be between fish and amphibian, which is the evolutionary double loop pathway.

a. is wrong since fish has only one circuit

b. is wrong since amphibians has 3 chamber hearts.

c. Right

d. doesn't sound very evolutionary to me.