To determine if the relationship between time walking and calories burned is proportional, we need to assess whether the ratio of calories burned to time is constant.
Let's calculate the ratio of calories burned to time for each entry:
- For 20 minutes: \( \frac{100}{20} = 5 \)
- For 30 minutes: \( \frac{150}{30} = 5 \)
- For 40 minutes: \( \frac{200}{40} = 5 \)
- For 60 minutes: \( \frac{300}{60} = 5 \)
- For 80 minutes: \( \frac{400}{80} = 5 \)
Since the ratio is constant at 5 for all time intervals, the relationship is indeed proportional.
Additionally, we can check whether the graph passes through the origin. When time is 0, if calories burned is also 0, it will pass through the origin, indicating that the relationship is proportional.
Based on this analysis, the correct answer is:
D. The relationship is proportional.