Correct option is A
Thevenin's theorem states that any linear, two-terminal electrical network can be simplified to an equivalent circuit consisting of a single voltage source in series with a resistor. This equivalent circuit makes it easier to analyze complex networks by reducing them to simple series or parallel circuits.
Thus, according to Thevenin’s theorem, a complex circuit can be replaced by a voltage source (Thevenin voltage) and a series resistor (Thevenin resistance) across the terminals of interest.
