2 When ...................................................... her grandparents?

Past Simple

1. When did Becky visit her grandparents?

Explanation: This question is asking about the time of an event in the past. The structure for a 'When' question in the past simple is: When + did + subject + base form of verb + object/complement? Based on the provided to-do list, 'visit grandparents' is an activity Becky might have done. The checkmark next to 'visit grandparents' in some versions of this exercise would confirm this, but here it's implied by the structure of the question and the options.