I'm not sure of my answer and pls help and explain

[mslazy]

During a complete bundle branch block, many ectopic pacemakers in the ventricles may take over the action of the SA node. The EKG may show which of the following?
A. Artial systole
B. Ventricular diastole
C. Ventricular bradycardia
D. Ventricular fibrillation

If there is a block of the electrical current at the AV node, this abnormality would show up as which of the following?
A. A longer duration of the QT interval
B. A longer duration of the PR interval
C. A larger amplitude of the R peak
D. A shorter amplitude of the P wave

Which of the following is FALSE about isovolumic ventricular contraction?
A. The amount of the blood in the ventricles during isovolumic ventricular contraction if the End Diastolic Volume
B. The amount of the blood in the ventricles during isovolumic ventricular is the volume of the blood that is pumped against an afterload pressure in the aorta
C. The volume of the blood in the ventricles during isovolumic ventricular contraction is equal to the amount of blood in the pulmonary trunk and aorta
D. The pressure in the ventricles during isovolumic ventricular contraction is equal to the pressure in the pulmonary trunk and aorta

During the ventricular systole, what happened to ventricular blood volume once the ventricular pressure exceeds the pressure in the aorta?
A. Blood volume stays the same (isovolumic volume)
B. Blood volume decreases
C. Blood volume increases

And why? (For the question above)
A. The ventricles relax
B. The aorta relaxes
C. The semi lunar valaves open
D. The atrioventricular valves open

[JackBean]

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