From the meaning of the question, it can be concluded that 0≤x≤4, 0≤y≤4,
When they emit light for the first time, the difference is less than 2 seconds, then |x-y|≤2,
The probability obtained by geometric probability is the ratio of the areas of the above two planes.
It can be seen from the figure that the probability is:16-2×12× 216 = 34.
So choose C.