Find the Zth for the given circuita.20-j10 ohmsb.10+j20 ohmsc. 20+j10 ohmsd.10-j20 ohms

The Zth (Thevenin's impedance) for the given circuits can be calculated as follows:

a. For a circuit with impedance of 20-j10 ohms, the Zth is simply the same, 20-j10 ohms.

b. For a circuit with impedance of 10+j20 ohms, the Zth is also the same, 10+j20 ohms.

c. For a circuit with impedance of 20+j10 ohms, the Zth is the same, 20+j10 ohms.

d. For a circuit with impedance of 10-j20 ohms, the Zth is the same, 10-j20 ohms.

In these cases, the Thevenin's impedance is equal to the impedance of the circuit because there are no other elements in the circuit. If there were other elements, such as resistors or capacitors in series or parallel, you would need to calculate the equivalent impedance taking into account these elements.