Which of the following is part of the 12 practices defined in eXtreme Programming (XP)?

In Scrum, the development team decides which events or ceremonies take place during a Sprint.

Part way through a project, several team members are in conflict over whether or not a deliverable has been properly completed. How should the agile leader reduce this conflict?

A Scrum team is refining product backlog items for the next sprint in a project. The product owner does not agree with the changes. Can the product owner reject changes to a product backlog?

Having problems does not indicate a problem in itself, so welcome problems because they bring with them the chance for the team to overcome, grow, and become stronger together." As an Agile Coach, which are the multiple perspectives to analyse to detect the symptoms for the problem?