Answer:
2-4 minutes
Step-by-step explanation:
Fastest changing temperature means larger change in temperature when subtracting final temperature from initial temperature in a given time period (given time period is 2 minutes for all the options)
For 0-2 minutes, our final temperature was 40 (at 2 min) and initial temperature was 20 (at 0 min), thus temperature change was only 20 C.
For 2-4, our final temperature was 80 (at 4 min) and initial temperature was 40 (at 2 min) thus temperature change was 40 C.
For 4-6, our final temperature was 100 (at 6 min) and initial temperature was 80 (at 4 min) thus temperature change was 20 C.
We are not given temperature at 8 min so option D is invalid.
As we can clearly see that in a given 2 minute period, option B has the fastest change because it changed 40C when compared to other options that changed only 20C from starting temperature.
Hope that makes sense.