Final answer:
In standard Scrum practice, the retrospective for a 4-week Sprint is typically three hours, but none of the provided options match this. Times can vary depending on the team and organization.
Step-by-step explanation:
The timebox for a retrospective in a 4-week Sprint is typically determined by the length of the Sprint and the guidelines provided by frameworks such as Scrum. The Scrum Guide suggests that for a one-month Sprint, or 4-week Sprint, the retrospective meeting should be timeboxed to a maximum of three hours. However, since the options provided do not include a length of three hours, we should consider the context or potentially any organizational adjustments to standard Scrum practice, as exact times can vary depending on the team and organization.