Final answer:
The Sprint Backlog contains the user stories a team is working on during a sprint, which is a time box of one to four weeks.
Step-by-step explanation:
The backlog that contains user stories a team may be working on is the c) Sprint Backlog. This is a subset of the Product Backlog, which is managed by the Product Owner and contains all potential work for the product. In contrast, the Sprint Backlog is managed by the development team and includes only those user stories that are selected for the current sprint, typically a time box of one to four weeks. The team commits to completing these user stories during the sprint. The Release Backlog and Team Backlog are not standard terms recognized in Scrum, which is the framework typically referenced in relation to these terms.