Blood Flow Pathway in the Heart

Steps:

• Deoxygenated blood enters right atrium (3).
• Pumps to right ventricle (4) for lung circulation.
• Oxygenated blood returns to left atrium (1).
• Flows to left ventricle (2) for systemic circulation.

Why B is correct:

• Sequence 3→4→1→2 follows the standard double-circuit path: right heart to lungs to left heart, per cardiac anatomy.

Why the others are wrong:

• A: Starts with left atrium (1) to ventricle (2), reversing deoxygenated entry.
• C: Begins with left ventricle (2) to atrium (1), opposing one-way valve flow.
• D: Jumps from right atrium (3) to left ventricle (2), bypassing pulmonary circuit.

Final answer: B