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In the figure, the LED—
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- Emits light when both S1 and S2 and closed
- Emits light when both S1 and S2 are open
- Emits light when only one of S1 or S2 is closed
- Does not emit light irrespective of the switch positions.
Correct Option: D
From figure we conclude that LED will emits light when the output of NAND gate is zero. In order to make the output of NAND gate 0, the output of AND gate and EX-NOR gate must be 1. Applying hit and trail method. Finally we conclude that alternative (D) is the correct choice.
