$21.$ TCP $($Transmission Control Protocol$)/$IP $($Internet Protocol$)$s technical governing body reserved a series of addresses for private networks this is networks whose hosts cannot be accessed directly through the Internet. Which one of the following is NOT a reserved address?a$.$For Class A$,$ all addresses beginning with $10$b$.$For Class B$,$ addresses from $172\mathrm{.}16$ to $172\mathrm{.}31$c$.$For Class C$,$ addresses from $201\mathrm{.}168\mathrm{.}0$ to $201\mathrm{.}168\mathrm{.}255$