Under which condition does the bipolar junction transistor(BJT) operate in the saturation region?

Correct option is D

​$$\text{A BJT operates in the saturation region when both junctions are forward-biased:} \\[8pt]\bullet \ \text{Emitter–base junction: forward-biased} \\[4pt]\bullet \ \text{Collector–base junction: forward-biased} \\[8pt]\text{In this region:} \\[6pt]\bullet \ \text{The transistor is fully ON} \\[4pt]\bullet \ \text{It conducts maximum current} \\[4pt]\bullet \ \text{It is commonly used as a switch in digital circuits}$$​​