Which answer best describes Wide Band Delphi (e. g. Planning Poker) estimating?

A.
Team members provide story estimates individually and discuss their reasoning until a
consensus on the estimate is reached.

B.
Team performance on prior projects is analyzed, and actual hours and durations are
used to determine estimates for similar user stories.

C.
Team members apply relative sizing to each task, and story points are triangulated
based on the other stories in the Sprint Backlog.

D.
Team members assign a realistic and a pessimistic estimate to each story, and points

are assigned based on the calculated average.