To determine which interval will have the highest bar on the histogram, we look at the frequencies for each interval:
- 0–4: 6
- 5–9: 10
- 10–14: 9
- 15–19: 12
- 20+: 9
The highest frequency is for the interval 15–19, which has a frequency of 12.
Therefore, the interval that will have the highest bar on the histogram is 15–19.