To determine if the relationship between the time walking (in minutes) and the calories burned is proportional, we need to check if the ratio of calories burned to time walking is constant for all the values given.
Let's calculate the ratio of calories burned to time walking for each entry:
- For 20 minutes: \( \frac{100 \text{ calories}}{20 \text{ minutes}} = 5 \)
- For 30 minutes: \( \frac{150 \text{ calories}}{30 \text{ minutes}} = 5 \)
- For 40 minutes: \( \frac{200 \text{ calories}}{40 \text{ minutes}} = 5 \)
- For 60 minutes: \( \frac{300 \text{ calories}}{60 \text{ minutes}} = 5 \)
- For 80 minutes: \( \frac{400 \text{ calories}}{80 \text{ minutes}} = 5 \)
Since the ratio is constant (5 calories per minute) for all time intervals, this indicates that the relationship is proportional.
Therefore, the correct response is: The relationship is proportional.