The correct answer is (d) Pisces only.
Explanation:
Fishes (Pisces) have a two-chambered heart, which only pumps deoxygenated blood to the gills for oxygenation. Once the blood is oxygenated in the gills, it then returns to the body, but it is still deoxygenated when it leaves the heart.
Why other options are incorrect:
(a) Pisces and amphibians:
While amphibians also have a three-chambered heart and experience some mixing of oxygenated and deoxygenated blood, they still manage to send some oxygenated blood to their bodies.
(b) Amphibians and reptiles:
Both amphibians and most reptiles have three-chambered hearts. While their hearts aren’t fully capable of separating oxygenated and deoxygenated blood completely, they still achieve a better separation than fish.
(c) Amphibians only:
This is incorrect because both Pisces (fish) and amphibians have three-chambered hearts.