Why is the value of %_COMPLETE refreshed to 13.59 in the third output after reaching 88.77?

View the Exhibit and examine the output of the query in different times when the following
command runs in an RMAN session:
RMAN> BACKUP DATABASE FILESPERSET 2;
The database has seven data files. Why is the value of %_COMPLETE refreshed to 13.59 in the
third output after reaching 88.77?

A.
Because the progress is reported for each data file

B.
Because the progress is reported for each backup set

C.
Because other RMAN sessions have issued the same BACKUP command

D.
Because new data files have been added to the database while the RMAN backup is in
progress