Answer:
I would say the 3rd one
Explanation:
t' = 458.26 μs
given,
distance traveled by the cosmic ray = 60 Km
time = 500 μs
time taken for the journey according to cosmic ray = ?
now,
v = 1.2 x 10⁸ m/s
according to time dilation formula
t' = 500 x 0.9165
I think that the answer is the first or third one