Answer:
(a) The horizontal ground reaction force 
(b) The vertical ground reaction force 
(c) The resultant ground reaction force 
Explanation:
Given
John mass , m = 65 kg
Horizontal acceleration , 
Vertical acceleration , 
(a) Using Newton's 2nd law in horizontal direction

=>
Thus the horizontal ground reaction force 
(b) Using Newton's 2nd law in vertical direction

=>
=>
Thus the vertical ground reaction force 
(c) Resultant ground reaction force is

=>
=>
Thus the resultant ground reaction force 
Light will travel more slowly in a material with a higher index of refraction
Send wave from your location to the object and wait until echo is back.
Measure the time taken.
If you know the speed of wave (say sound wave), than just multiply by half time taken wave to return
Answer:
I think it is the forth one