Explanation/Reference:
127.0.0.1 is the IPv4 loopback address.

Explanation/Reference:
Since the leftmost three bits are reserved as "001" for Global unicast IPv6 addresses, the range of Global Unicast Addresses available now are from 2000 to 3FFF.
21DA is a global unicast prefix.

Explanation/Reference:
The speed of a Wi-Fi wireless network connection depends on several factors.
Like most kinds of computer networks, Wi-Fi supports varying levels of performance depending on which technology standards it supports. Each Wi-Fi standard is rated according to its maximum theoretical network bandwidth:
A Wi-Fi network connection operates at the highest possible speed that both devices (endpoints) can support.
An 802.11g laptop connected to an 802.11n router, for example, will network at the lower speeds of 'g'.

Explanation/Reference:
B: Ethernet networks can use coax, twisted-pair, or fibre optic cabling.
C: Ethernet is the most widely used network topology.
E: Speed can be negotiated on Ethernet network.
Incorrect:
not A: Tokes is used in ring topologies. The two possible topologies for Ethernet are bus and star.
Not D: A network topology is not a protocol. Switching can be performed on Ethernet networks.