Answer:
Sentence 2.
Explanation:
A shift in the verb form is when the tense of the verb in the first sentence is different from the verb tense in the next. This change in the form of the verb is known as a shift in the verb tense.
Considering the given sentences, the verb in sentence 1 is "went", which is in the past tense. The verb "buy" in sentence 2 is in the present tense while sentence 3's verb "realized" is in the past tense.
So, the verb changed from past-present-past tense. Thus, the sentence 2 contains the shift in the verb tense.