Question

Which one is the first heart sound.
(1) Lubb during closure of semilunar valves
(2) Lubb during closure of atrioventricular
(3) Dub during closure of atrioventricular valves
(4)Dub during closure of semilunar valves.

Answer 1

it's option 2

first heart beat lub occurs when tricuspid and bicuspid valves close.

hope this ans may help you....

Answer 2

Here is your answer~

Lubb during closure of atrioventricular