The best possible Answer is c
Have you tried to look this up on Quizlet. I just had a similar question on one on my quizzes & the whole test was on Quizlet
Answer:
The hunter should aim directly at the perched monkey because the tranquilizer dart will fall away from the line sight at the same rate that the monkey falls from its perch.
Tan theta = 9 / 90 = .1 so theta = 5.71 deg
The time for the monkey to reach the ground is
t = (2 h / g)^1/2 = (18 / 9.8)^1/2 = 1.36 sec
So the horizontal speed of the dart must be at least
Vx = 90 m / 1.36 sec = 66.4 m/s
Vx = V cos theta
V = 66.4 m/s / cos 5.71 = 66.7 m/s