Which statement is true?

In the exhibit Router A and Router B are operating on the LAN with Router B acting as the designated intermediate system (DIS).

When Router C and Router D are added to the LAN. Which statement is true?

A.
Router C becomes the new DIS with no backup DIS.

B.
Router D becomes the new DIS with no backup DIS.

C.
Router C becomes the new DIS with Router B as the backup DIS.

D.
Router D becomes the new DIS with Router A as the backup DIS.