$$ \text { Refer to the four circuits shown. } $$

Which one of the following options for $\mathrm{k}_1, \mathrm{k}_2, \mathrm{k}_3$, and $\mathrm{k}_4$ makes all of them realizable?

$$ \text { The I-V characteristics of the elements between the nodes } X \text { and } Y \text { is best depicted } $$

A nullator is defined as a circuit element where the voltage across the device and the current through the device are both zero. A series combination of a nullator and a resistor of value, $R$, will behave as a

The number of junctions in the circuit is