Which of the following IP addresses are valid Class B host addresses if a default Class B mask is in use?

Which of the following IP addresses are valid Class B host addresses if a default Class B mask is
in use? (Choose two.)

A.
10.6.8.35

B.
133.6.5.4

C.
192.168.5.9

D.
127.0.0.1

E.
190.6.5.4

Explanation:
The IP addresses 133.6.5.4 and 190.6.5.4 are both valid Class B addresses when a default mask
is in use.
The Class B default mask is 255.255.0.0 and the range of valid addresses is 128.0.0.0-
191.255.255.255.
The IP address 10.6.8.35 is a Class A address. The Class A default mask is 255.0.0.0 and the
range of valid addresses is 1.0.0.0 – 127.255.255.255, with the exception of the range 127.0.0.1
– 127.255.255.255, which is reserved and cannot be assigned.
The IP address 192.168.5.9 is a Class C address. The Class C default mask is 255.255.255.0 and
the range of valid addresses is 192.0.0.0 – 223.255.255.255.
The IP address 127.0.0.1 is a Class A address, but it comes from a reserved portion that cannot
be assigned.
The range 127.0.0.1 – 127.255.255.255 is used for diagnostics, and although any address in the
range will work as a diagnostic address, 127.0.0.1 is known as the loopback address. If you can
ping this address, or any address in the 127.0.0.1 – 127.255.255.255 range, then the NIC is
working and TCP/IP is installed. The Class A default mask is 255.0.0.0 and the range of valid
addresses is 1.0.0.0 – 127.255.255.255, with the exception of the range 127.0.0.1 –
127.255.255.255, which is reserved and cannot be assigned.