A. Arteries
B. Muscle fibres
C. Nerves
D. Veins
✅ The correct answer is option D.
Veins act as a channel of transmission of blood to the heart in the human body. Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. As the atrium contracts, blood flows from your right atrium into your right ventricle through the open tricuspid valve.
Veins act as a channel of transmission of blood to the heart in the human body. Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. As the atrium contracts, blood flows from your right atrium into your right ventricle through the open tricuspid valve.