The correct answer is option 'A', the right auricle. Let's explain why.

The heart is a muscular organ that pumps blood throughout the body. It is divided into four chambers: two atria (auricles) and two ventricles. The right atrium receives deoxygenated blood from the body through the superior and inferior vena cava, which are large veins that bring blood back to the heart from the systemic circulation.

Here is a step-by-step explanation of how blood flows through the heart:

1. Deoxygenated blood enters the right atrium: The superior and inferior vena cava bring deoxygenated blood from the body to the right atrium. The right atrium is one of the two atria in the heart.

2. Right atrium contracts: When the right atrium contracts, it pushes the blood into the right ventricle through the tricuspid valve. The tricuspid valve prevents the backflow of blood into the right atrium.

3. Right ventricle receives blood: The right ventricle is the chamber of the heart that receives blood from the right atrium. It is responsible for pumping deoxygenated blood to the lungs for oxygenation.

4. Right ventricle contracts: When the right ventricle contracts, it pushes the deoxygenated blood through the pulmonary valve and into the pulmonary artery. The pulmonary artery carries the blood to the lungs.

5. Blood reaches the lungs for oxygenation: In the lungs, the deoxygenated blood picks up oxygen and gets rid of carbon dioxide through the process of respiration. Oxygenated blood then returns to the heart through the pulmonary veins.

6. Oxygenated blood enters the left atrium: The oxygenated blood from the lungs enters the left atrium of the heart through the pulmonary veins. The left atrium is the other atrium in the heart.

7. Left atrium contracts: When the left atrium contracts, it pushes the oxygenated blood into the left ventricle through the mitral valve (also known as the bicuspid valve). The mitral valve prevents the backflow of blood into the left atrium.

8. Left ventricle receives blood: The left ventricle is the chamber of the heart that receives blood from the left atrium. It is responsible for pumping oxygenated blood to the rest of the body through the systemic circulation.

From the above explanation, we can conclude that the blood from the systemic circulation, which is deoxygenated blood, first comes to the right atrium or auricle of the heart.

In amphibians, reptiles, birds, and mammals, blood flow is directed in two circuits: one through the lungs and back to the heart, which is called pulmonary circulation, and the other throughout the rest of the body and its organs including the brain (systemic circulation)