The answer is D. All of these
Answer:2t
Explanation:
Given
Jason throwing watermelon at speed v and it spend t time in air
time to reach max height

0=v-gt'

and time to reach bottom is also t'
t=2t'

For guy throws his watermelon at speed 2v
So total time in air will be


t''=2t
The frequency of the wave has not changed.
In fact, the frequency of a wave is given by:

where v is the wave's speed and
is the wavelength.
Applying the formula:
- In air, the frequency of the wave is:

- underwater, the frequency of the wave is:

So, the frequency has not changed.