The correct answer is option 2: William Harvey. He was the scientist who first explained about blood circulation. William Harvey, an English physician, made this groundbreaking discovery in the 17th century. Prior to his research, people believed that blood was consumed by the body and then produced again. However, Harvey`s studies challenged this belief and provided evidence for the circulation of blood through the heart and body. He conducted experiments on animals and observed the movement and flow of blood. Harvey`s work revolutionized the understanding of human physiology and laid the foundation for modern medicine. He is recognized as one of the most important figures in the history of biology and medicine.