In a rabbit,the opening of the post caval vein into the right auricle is guarded by:

$SAN$ generates an action potential which stimulates both the $A$ to undergo a simultaneous contraction called $B$. This increases the flow of the blood into the ventricles by about $C$ percentage. Choose the correct option for $A, B$ and $C$.

Which is the pacemaker of the frog's heart?

The circulation of blood was discovered by .....

Heart murmurs are indicative of a defect in which of the following?

Match the items given in Column-$I$ with those in Column-$II$ and select the correct option given below:

Column-$I$	Column-$II$
$(a)$ Tricuspid valve	$(i)$ Between left atrium and left ventricle
$(b)$ Bicuspid valve	$(ii)$ Between right ventricle and pulmonary artery
$(c)$ Semilunar valve	$(iii)$ Between right atrium and right ventricle