A revolving rifle fires 9mm bullets. As the bullets travel down the barrel of the rifle, their speed is given by the equation v=(-5.15×10^7)t2+(2.30×10^5)t, where v is in meters per second and t is the time. How can the speed of the bullets be described?

A. The speed of the bullets increases as time increases.
B. The speed of the bullets decreases as time increases.
C. The speed of the bullets remains constant as time increases.
D. The speed of the bullets fluctuates as time increases.