The first heart sound is described as lub and corresponds to which event of the cardiac cycle?

The first heart sound correspond to the closure of atrioventricular valves which comprises of mitral and transcupid valves.

Explanation:

The first heart sounds is describe as lub and its correspond to the closure of atrioventricular valves which comprises of mitral and triscupid valves because it's coincides with ventricular contractions as the ventricular pressures surpasses the pressure of the atrial which mark the begining of ventricular systole and the end of mechanical diastole. It is a single sound because the mitral and triscupid valves closes simultaneously.

sulfur dioxide

explanation: acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. these substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.

answer: b

coz red blood cells marrow and circulates the body for 120 days.