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

The apex beat of the heart is synchronous with:

$A$: The cardiac impulse which originates from $SA$ node in mammalian heart cannot spread directly from atria to ventricles.
$R$: In mammalian heart there is no continuity between cardiac muscle fibres of atria and those of ventricles except $AV$ bundles.

The $lubb$ and $dubb$ heart sounds are produced due to:

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

If due to some injury the chordae tendinae of the tricuspid valve of the human heart is partially non-functional,what will be the immediate effect?