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The cardiac cycle consists of two phases; a period where the heart muscle is relaxed, called diastole, and a period of contraction, called systole.

These are then divided into four stages. These are;

1. Ventricular Filling Period (VPF)

2. Isovolumetric Contraction Period (ICP)

3. Ventricular Ejection Period (VEP)

4. Isovolumetric Relaxation Period (IRP)

At rest, cardiac diastole lasts for approximately 0.5 seconds, and cardiac systole lasts approximately 0.3 seconds to complete. However, during exercise, when the heart rate is increased the time period of diastole , especially, is reduced.

Hope this helps!

i can't answer your question in very sad situation.

but if your situation is very bad, then you can find happiness by thinking about your past that has full of happiness.

or you should do meditation for some time to get rid off from that bad situation.

the correct answer is d