While sizing a user story in planning poker, one team member believes the user story...

Comprehensive and Detailed Explanation:

Significant estimation discrepancies often indicate a lack of clarity. The story may be ambiguous or too broad. In agile practices, the team should ask the product owner to refine the story so it can be better understood and estimated with greater accuracy.

A (averaging) is not an agile practice.

C may be helpful but not sufficient in real time.

D is arbitrary and ignores team consensus.

B supports agile practices like backlog refinement.