what is the definition of Extract lag?

In GoldenGate terms, what is the definition of Extract lag?

A.
The difference in time between when a change is made to source data and when that change is
reflected in the target data.

B.
The difference in time between the current times at the target system.

C.
The difference in time between when a change record is received at the target system and
when the change is reflected in the target data.

D.
The difference in time between when a change record is processed by the extract and the
timestamp of the record in the data source.

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