Which valve is located between the left atrium and the left ventricle?

Oxygenated blood is carried by

Given below are two statements.
Statement $I$ - The heart sound $Dub$ is heard during ventricular diastole.
Statement $II$ - The heart sound $Lubb$ is heard during atrial systole.
In the light of above statements,select the correct option given below:

The bundle of $HIS$ is a network of which of the following?

What is the significance of the atrio-ventricular node and atrio-ventricular bundle in the functioning of the heart?

Bradycardia indicates slow heart rate, generally below . . . . . . per minute. (in $beats$)