In the given diagram, which chambers contract together?
A and B
C and D
The given chambers of the heart are as follows:
A: Right atrium
B: Left atrium
C: Right ventricle
D: Left ventricle
The atria relax while they fill with blood. Then they contract simultaneously and pump the blood to the ventricles on their respective sides. Then the ventricles contract and pump the blood to the different parts of the body.