Final answer:
The flow rate increases when the left flow tube radius is increased, as dictated by Poiseuille's law, which states that flow rate depends on the fourth power of the vessel's radius.
Step-by-step explanation:
When the left flow tube radius was increased, the correct answer is . According to principles of fluid dynamics, specifically Poiseuille's law, the flow rate is proportional to the fourth power of the radius of the tube. This means even a small increase in the radius of a blood vessel (such as an artery or arteriole) will lead to a relatively large increase in the flow rate of the blood through that vessel, assuming other factors such as viscosity and length remain constant.
Additionally, this question must not be confused with stroke volume, which refers to the amount of blood pumped by the left ventricle of the heart with each beat and is not directly related to changes in the radius of the blood vessels. Resistance in blood vessels is a major determinant of flow rate, and resistance decreases as the radius increases.