When would you use the PASSTHRU parameter?

When would you use the PASSTHRU parameter?

A.
When using a data pump to distribute all of the trail data “as is” to a remote system.

B.
When Extract is processing database transaction logs where you have a remote database connection.

C.
For a SPECIALRUN one-time processing task that is doing an initial load.

D.
When Extract is processing database transaction logs and writing to a local trial that will be read by a local Replicat.

Explanation:
http://download.oracle.com/docs/cd/E15881_01/doc.104/gg_wux_ref_v104.pdf