The heart of an elephant is

Following are the stages of the pathway for the conduction of an action potential through the heart:
$A.$ $AV$ bundle
$B.$ Purkinje fibres
$C.$ $AV$ node
$D.$ Bundle branches
$E.$ $SA$ node
Choose the correct sequence of the pathway from the options given below:

In humans,the heart rate of $72$ beats/minute is regulated by which of the following?

The histology of the heart superficially shows the following structures, $EXCEPT$:

The tricuspid valve is found in .............

Given below are two statements.
Statement $I$: Visceral layer of serous pericardium forms the outer wall of human heart.
Statement $II$: Epicardium is formed of a thick layer of cardiac muscles.
In the light of the above two statements,choose the correct answer from the options given below.