List of top Network Theory Questions on Impedance

Given below are two statements, one is labelled as Assertion (A) and the other is labelled as Reason (R):
Assertion (A): In an impedance, Smith chart point r =0, x=0 represents open-circuit point. 
Reason (R): In an impedance, Smith chart, √r = -1 and √i = 0 represents r = 0 and x = 0. 
In the light of the above statements, choose the correct answer from the options given below.

If Port-2 of a 2-port network is terminated with 73 Ω and ABCD parameter of 2-port network are A=C=3, B=5 and D=-2; input impedance of that network is

For the circuit given below, Thevenin's equivalent impedance $(Ζ_{τh})$ of the circuit is given as