She asks the pupil to explain how he obtains those values.
The pupil shows the pattern: 21 = 2 × 1 = 2, 22 = 2 × 2 = 4, so 20 = 2 X 0 = 0.
Then, the teacher challenges him with 23 etc. This causes cognitive conflict
for the pupil, and he is given some time to think about the conflict and learn from him
mistakes.