Contraction of the right ventricle of the human heart pumps blood into the......

In birds and mammals,the oxygenated blood is received by ...$A$... and deoxygenated blood is received by ...$B$.... The ventricles pump it out without any mixing of oxygenated and deoxygenated blood. Choose the correct option for $A$ and $B$.

The inter-auricular septum in embryonic stages has a/an:

Define/Explain: $(1)$ Semi-lunar valve.

The $Bundle$ $of$ $His$ are:

Since it is the sinu-auricular node which initiates the impulses in the heart of a mammal,it is called: