Explanation:

The human heart is a vital organ responsible for pumping blood throughout the body. It is a muscular organ divided into distinct compartments to efficiently separate oxygenated and deoxygenated blood and pump them to the systemic and pulmonary circulations, respectively. Option (A) is correct because the human heart consists of four chambers: two upper chambers called atria (singular: atrium) – the right atrium and the left atrium – and two lower chambers called ventricles – the right ventricle and the left ventricle. Option (B) is incorrect; A three-chambered heart is found in amphibians and most reptiles. Option (C) is incorrect; A two-chambered heart is characteristic of fish. Option (D) is incorrect; No vertebrate has a single-chambered heart, as it would be inefficient for circulation.