Final answer:
The correct punctuation for the sentence is option 2) who promised us. In this sentence, the phrase 'who promised us' is essential to the meaning of the sentence and should not be set off by commas.
Step-by-step explanation:
The correct punctuation for the sentence is option 2) who promised us.
In this sentence, the phrase 'who promised us' is essential to the meaning of the sentence and should not be set off by commas. Commas should only be used to set off non-essential phrases or clauses.
Here is the corrected sentence: To reduce the resulting quarrels, we both met with Grandma who promised us that we'd each have special activities.