Figure shows a circuit designed to control a lamp. For what positions of the switches `S_(1)` and `S_(2)` will the lamp the lit?

Options

A. `{:(S_(1),S_(2)),("closed","closed"):}`
B. `{:(S_(1),S_(2)),("closed","open"):}`
C. `{:(S_(1),S_(2)),("open","closed"):}`
D. `{:(S_(1),S_(2)),("open","open"):}`

Answer

D

Explanation

The truth table of the `HAND` gate is as shown below:
`|(S_(1),S_(2),Output),(0,0,1),(0,1,1),(1,0,1),(1,1,0)|`
Where a level `0` at the input, `S_(1)` or `S_(2)` corresponds to a closed switch (at `0V`) and a logic level `0` at the output means the lamp will be lit. From the truth table, both switches `S_(1)` and `S_(2)` have to be at open position in order to light up the lamp at the output of the `HAND` gate.