They want to use the numbers 0-9
Count the number of timers a color shos on the wheel and assign 1 number for each time the color shows:
Blue shows 4 times so you would assign blue the numbers: 0,1,2,and 3
There are 3 yellows so you would assign that 4, 5, and 6
There are 2 reds so , 7 and 8
and 1 green would be 9
Answer is D.