What do the regexp_pattern and regexp_replace_string parameters accomplish?

What do the regexp_pattern and regexp_replace_string parameters accomplish?

A.
They find a pattern of nine digits; break the digits into three groups that contain the first three,
the next two and then the last four digits; and replace all digits with XXXXX concatenated with the
last four digits.

B.
They find a pattern of six digits; break the digits into two groups that contain the first five, and
then the last digit; and replace all digits with XXXXX concatenated with the last digit.

C.
They find a pattern of nine digits and display the digits as XXXXX XX XXXX.

D.
They find a pattern of nine digits and display the first five digits as XXXXX and the last four
digits as 3333.