Answer:
The correct option is D.
Explanation:
It is given that the volume, in gallons, in the trough after it has been unplugged can be modelled by

Where, t is time, in minutes.
It is a quadratic function with positive lending coefficient. It means it is an upward parabola.
The minimum value represents the minimum volume at time t.
Since it is an upward parabola, therefore it has no maximum point.
y-intercept represents the initial volume in gallons.
Zero represents the time at which the volume is 0 or the time in which trough is drained.
Therefore the correct option is D.