This list shows the number of years that 99 u. s. supreme court justices served. 0 4 6 8 13 15 18 22 26 31 1 4 6 9 13 15 19 23 26 32 1 4 6 9 14 16 19 23 27 33 2 5 7 9 14 16 20 23 28 33 2 5 7 10 14 16 20 23 28 33 2 5 7 10 14 16 20 23 28 34 3 5 7 10 15 17 20 24 29 34 3 5 8 11 15 17 20 24 30 34 3 5 8 13 15 18 21 26 30 36 4 5 8 13 15 18 21 26 31 what number of years is the mode the supreme court justices served? a. 20 b. 15 c. 23 d. 5