Which of the following pathways shows the correct direction of blood flow through a double circulatory system, starting from the site of gas exchange in the lungs?
lungs→left side of heart→body organs→right side of heart\text{lungs} \rightarrow \text{left side of heart} \rightarrow \text{body organs} \rightarrow \text{right side of heart}lungs→left side of heart→body organs→right side of heart
lungs→right side of heart→body organs→left side of heart\text{lungs} \rightarrow \text{right side of heart} \rightarrow \text{body organs} \rightarrow \text{left side of heart}lungs→right side of heart→body organs→left side of heart
lungs→left side of heart→right side of heart→body organs\text{lungs} \rightarrow \text{left side of heart} \rightarrow \text{right side of heart} \rightarrow \text{body organs}lungs→left side of heart→right side of heart→body organs
lungs→body organs→left side of heart→right side of heart\text{lungs} \rightarrow \text{body organs} \rightarrow \text{left side of heart} \rightarrow \text{right side of heart}lungs→body organs→left side of heart→right side of heart