Which vein contains the oxygenated blood in humans?

What is the normal heart rate in a two-month-old infant?

Which structure is formed from the bundle of His?

What is the cardiac output produced by a normal heart?

The 'dubb' heart sound is produced at the time of closure of:

When a frog's heart is taken out of the body, it continues to beat for some time. Select the best option from the following statements.
$(1)$ Frog is a poikilotherm.
$(2)$ Frog does not have any coronary circulation.
$(3)$ Heart is "myogenic" in nature.
$(4)$ Heart is autoexcitable.