Answer:

Step-by-step explanation:
Since there are a total of 4 colors, and there are 5 of each colors, the total marbles in the bad would be;
5 x 4 = 20
If a color is selected at random the probability would be

our part is 5
our whole is 20
so the probability would be;
or
when reduced
Hope this helps!
The answer is D. If you substitute those values for n, you should be able to find that 4 makes the expression equal to 6.