Answer:
(a) Increase 16 times
Step-by-step explanation:
According to the Poiseuille flow equation the rate of flow of fluid is directly related to four time square of the radius of the vessel.

Here, F is the rate of flow, and r is the radius of vessel.
Now according to the question diameter is increased by 2 times then radius is also increased by two times than radius becomes 2r.
So put this value in the flow equation.

Therefore, the rate of flow is increased by 16 times.