Which one of the following is the Boolean expression for $NOR$ gate?

The following figure shows a logic gate circuit with two inputs $A$ and $B$ and the output $Y$. The voltage waveforms of $A$,$B$,and the output $Y$ are as given. The logic gate is:

The output of an $OR$ gate is $1$:

The combination of gates shown below yields:

In the following digital circuit, the output '$Y$' will be '$1$' for inputs '$A$' and '$B$' having values:

In the circuit below,$A$ and $B$ represent two inputs and $C$ represents the output.