Question

The output of OR gate is 1:-
(A) If either one or both inputs are 1
(B) Only if both inputs are 1
(C) If either input is zero
(D) If both the inputs are zero

Answer 1

Hint
An OR gate is a logical gate that has two or more inputs that can give an output of $1$ which is called high or $0$ which is called low. The output of an OR gate comes back low only when all the inputs attached to the OR gate have their value low. In all other situations, the output of the OR gate is one.

Complete step by step answer
An OR gate is a logical gate through which logical disjunction is implemented. The output of an OR gate follows according to its truth table.
A two-input OR gate is denoted by the symbol,

Where $A$ and $B$ are the two inputs to the OR gate and $O$ is the output.
Now, the truth table of an OR gate is given by,

$A$	$B$	$O$
$0$	$0$	$0$
$1$	$0$	$1$
$0$	$1$	$1$
$1$	$1$	$1$

Now from the truth table, we can see that the OR gate has its output high when any one of the inputs or both the inputs of the OR gate is high. And the only time that the OR gate has a low output is when both the inputs of the OR gate are low.
So in the question, we are asked when the output of the OR gate is high or 1. So, the answer will be when either one of the inputs or both the inputs are high or 1.
So, the correct answer is option (A).

Note
The logic gates are like the building blocks of digital electronics and the OR gate is one of the basic logic gates. An OR gate can be used in many cases for example in industrial situations where one or more than one event needs to be detected. There are many other logic gates present whose applications depend on their truth table or their mode of operation.