Which vein contains the oxygenated blood in humans?

Where is the pericardial fluid secreted from?

Given below are two statements.
Statement $I$: Visceral layer of serous pericardium forms the outer wall of human heart.
Statement $II$: Epicardium is formed of a thick layer of cardiac muscles.
In the light of the above two statements,choose the correct answer from the options given below.

$A$ heart murmur occurs due to a defect in:

The $lubb$ and $dubb$ heart sounds are produced due to:

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