The correct option will be
D. Time, initial velocity and final velocity
The Formula can be written as,
Acceleration=Final velocity-Initial Velocity/Time
Vt = Vboat - Vriver
Vt = 18 - 2.5 = 15.5 m/s
If the boat's direction is the same as the water, you sum the velocities of the river and the boat .
They both make a thing go faster and slower but the relationship is force.
32 kg m/s would be the kinetic energy.