One feature that amphibians and humans have in common is

Both have two circuits for circulation.

Explanation:

The two circuits of circulations are known as the systemic circuit and the pulmonary circuit. In the systemic circuit oxygenated blood from the heart is pumped to all parts of the body through the blood vessels and then the blood is pumped back to he heart. In the pulmonary circuit deoxygenated blood from all parts of the body is pumped from the heart to the lungs to be oxygenated and after it is oxygenated it is pumped back to the heart.