Just prior to atrial contraction,
A. all four chambers are at rest and AV valves are open.
B. all four chambers are at rest and AV valves are closed.
C. all four chambers are contracting and all valves are open.
D. both ventricles are contracting and blood is being ejected into the major arteries.
E. both atria are contracting and blood is being ejected into the major arteries.
A
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