Which of the following produces the first heart sound?
the closing of the valves between the ventricles and the body
the opening of the valves between the atria and the ventricles
the closing of the valves between the atria and ventricles
the opening of the valves between the ventricles and the body

The closing of the valves between the atria and ventricles.

Explanation:

Heart sounds are defined as noises made by the beating heart and blood flow through heart. The S1 or first heart sound is generated by turbulence due to closing of two components, mitral valve and tricupsid valve.

The mitral valve and tricupsid valve are generally known as atrioventricular valves as they present between the atria and ventricles.

S1 sound is has low frequency, which is described as 'lub' and generates at the beginning of systole

Thus, the correct answer is third option.

9.9 years

a = p(1 + rt) . . account balance after time t at rate r starting with principal p

3000 = 2500(1 + 0.0202t) . . filling in the given numbers

1.2 = 1 + 0.0202t . . divide by 2500

0.2 = 0.0202t . . . subtract 1

0.2/0.0202 = t ≈ 9.901

it will take about 9.9 years for the account balance to reach $3000.