**Short-Circuited Impedance**

When an impedance is short-circuited, it means that the impedance is connected directly across a short circuit. In this case, the impedance value is effectively bypassed, and the current flowing through it becomes maximum while the voltage across it becomes zero.

Given that the short-circuited impedance is 5 ohms, it means that when the impedance is short-circuited, the current flowing through it is at its maximum value.

**Open-Circuited Impedance**

When an impedance is open-circuited, it means that the impedance is connected across an open circuit. In this case, the impedance value is effectively disconnected, and the current flowing through it becomes zero while the voltage across it becomes maximum.

Given that the open-circuited impedance is 20 ohms, it means that when the impedance is open-circuited, the current flowing through it is zero.

**Characteristic Impedance**

The characteristic impedance is the impedance that a transmission line presents to a signal when it is terminated with its characteristic impedance at the receiving end. It is a measure of how the transmission line behaves when a signal propagates through it.

In this case, we are given the short-circuited impedance and the open-circuited impedance. To find the characteristic impedance, we can use the relationship:

Characteristic Impedance = √(Short-Circuited Impedance × Open-Circuited Impedance)

Substituting the given values:

Characteristic Impedance = √(5 ohms × 20 ohms)
= √(100 ohms)
= 10 ohms

Therefore, the characteristic impedance is 10 ohms, which corresponds to option B.

Characteristic impedance=√(Z short circuit * Z open circuit)