What type of RJ45 UTP cable is used between switches?

Correct Answer: B) Crossover cable

Here's why:

Imagine two switches are like two people trying to talk.

* Option A: Straight-through cable: Think of this like both people trying to speak at the same time and both listening at the same time. They can't hear each other because their "talking" (transmit) lines are connected to each other and their "listening" (receive) lines are connected to each other. It doesn't work for two switches directly connected.

* Option B: Crossover cable: This cable is specially wired so that one person's "talking" (transmit) goes to the other person's "listening" (receive), and vice-versa. This is exactly what you need when connecting two switches directly!

* Option C: Crossover with a CSU/DSU: A CSU/DSU is a device used for connecting to a WAN (Wide Area Network) link, like a T1 line. It's not needed for connecting two switches locally.

* Option D: Crossover with a router in between the two switches: You wouldn't use a crossover cable *with* a router between the switches. The router acts as an intermediary and handles the signal routing. Routers typically use straight-through cables to connect to switches.

In summary: When you directly connect two switches, they need a crossover cable to make sure the transmit (talking) and receive (listening) lines are properly matched.