Question

which chambers contract simultaneously?
a two atria
b right atrium and right ventricle
c all chambers contract simultaneously.
d all chambers contract individually.

Explanation:

In the cardiac cycle, the two atria (left and right atrium) contract simultaneously. This is followed by the contraction of the two ventricles (left and right ventricle) simultaneously. So, option A is correct. Option B is incorrect as atrium and ventricle do not contract at the same time. Option C is wrong because atria and ventricles have different contraction times. Option D is incorrect as atria contract together and ventricles contract together.

Answer:

A. Two atria