The heart has four chambers and, within them, blood normally circulates in only one direction: from the right atrium to the right ventricle and from the left atrium to the left ventricle. A certain disease sometimes allows the flow to occur in the opposite direction, that is, it passes from the left ventricle to the left atrium. This disease affects 2% to 3% of the population and rarely produces serious heart problems. Some patients have symptoms such as chest pain, fatigue, palpitation and dizziness. Which heart structure is affected by this disease. How did you reach that conlucsion?

Likely an issue with the mitral valve.

Explanation:

If I read this correctly, you are likely referring to mitral regurgitation, which is a process where your mitral value does not close tightly enough to stop the blood to flow into left atrium.

Normally, when the left ventricle is full, the mitral valve shuts to prevent blood blood from flowing backward into the atrium while the ventricle contracts, and this allows for blood to go to aorta and to body. According to question since the process is reversed, I am gonna go out on a limb and say mitral valve is likely the structure affected by this since and how I came to conclusion is all the explaintion I did earlier.

i think   the answer is c hope i'm right

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.