hevenin resistance Rth is found [ ]

(A) by removing voltage sources and replace with their internal resistances
(B) by short-circuiting the given two terminals
(C) between any two open terminals
(D) between same open terminals as for Eth

The answer is "A".

The correct answer is (A) by removing voltage sources and replacing them with their internal resistances.

To find the Thevenin resistance (Rth), we need to follow these steps:

1. Remove all voltage sources in the circuit and replace them with their internal resistances. This is because we are trying to find the equivalent resistance seen from the terminals of the circuit, and by removing the voltage sources, we eliminate their effects on the circuit.

2. Short-circuit the two terminals of the circuit. This is done by connecting a wire or a piece of conducting material between the two terminals. By short-circuiting the terminals, we create a closed path for the current to flow through.

3. Calculate the total resistance seen from the short-circuited terminals. This can be done by adding up all the resistances in the circuit, including the internal resistances of the voltage sources that were replaced in step 1.

4. The obtained resistance is the Thevenin resistance (Rth) of the circuit. It represents the equivalent resistance seen from the terminals of the circuit when all the voltage sources are replaced by their internal resistances.

So, the correct option is (A) by removing voltage sources and replacing them with their internal resistances.