Which configuration completes this task?

A network administrator has been asked to configure the most specific aggregate route to
summarize the four specific prefixes shown below: Which configuration completes this task?

A.
[edit routing-options] user@router# show aggregate { route 10. .0.0/19; }

B.
[edit routing-options] user@router# show aggregate { route 10. .0.0/20; }

C.
[edit routing-options] user@router# show aggregate { route 10. .0.0/21; }

D.
[edit routing-options] user@router# show aggregate { route 10. .0.0/18; }

Explanation: