New work during a sprint

Hi,

could you please help me with the following question?

During a Sprint, when is new work or further decomposition of work added to the Sprint Backlog?
1. When the Product Owner identifies a new work.
2. As soon as possible after they are identified
3. When the Scrum Master has time to enter them.
4. During the Daily Scrum after the Development Team approves them.


Thanks in advance :-)