Why would a tester want to substitute a datapool candidate?

A.
A new value can be provided for each virtual tester, to ensure more realistic playback.

B.
A new value can be captured for each session, to ensure more realistic recording.

C.
The data correlation will fail if the candidate is not substituted with the value returned by the
server.

D.
The datapool will never get filled up with data unless it is connected to the test at playback time.