In which of the following gates, the output is 1, if and only if at least one input is 1?
Answer: Option C
In OR gate we need at least one bit to be equal to 1 to generate the output as 1 because OR means any of the condition out of two is equal to 1 which means if at least one input is 1 then it shows the output as 1. The number of 1's in input may be more than one but the output will always be 1 in OR gate. So the answer is 'C'.