Right atrium: Coronary sinus:: Left atrium: . . . . . . .

The nerve-like modified muscle in the right auricle is known as:

Purkinje fibers are located in the following structure/s:

All arteries carry oxygenated blood, except:

$SA$ node (Sinoatrial node) ke baare mein sahi kathan chuniye:
$I$. Located at the right upper corner of the right atrium.
$II$. Heart of heart.
$III$. It initiates the rhythmic contractile activity of the heart.
$IV$. It is called the pace-keeper of the heart.
$V$. It is called the pacemaker of the heart.
Which of the following options contains the correct statements?

In which chamber of the heart is more blood present?