The heart sound can be heard by using this instrument.

Blood pressure in the pulmonary artery is

How can the origin and conduction of the heartbeat be represented?

In which one of the following pairs do the two items mean one and the same thing?

All vertebrates possess a ...$A$.... Fishes have a ...$B$... chambered heart with atrium and ventricles. Amphibians and reptiles have a ...$C$... chambered heart. Birds and mammals have ...$D$... chambered heart.
Choose the correct option.

The heart continues beating normally even when its nervous supply is completely obliterated because it is