$(4)$

IT$351.$A$01\_1243[$Based on CompTIA Network $($N$10-00$;

Which of the following masks should the users use on point$-$to$-$point WAN links in order to reduce the waste of IP addresses on a network?

A $\frac{0}{28}$

B $129$

C $130$

D

$\frac{?}{31}$

E

$\frac{?}{27}$