Which of the following figure represents forward bias diode?

An AND gate is followed by a NOT gate in series. With two inputs ' $A$ ' and ' $B$ ', the Boolean expression for the output ' Y ' will be

If p-n junction diode is forward biased, then

In a certain 2 -inputs logic gate, when inputs $\mathrm{A}=0$ and $\mathrm{B}=0$, then output $\mathrm{C}=1$. And also when inputs $\mathrm{A}=0, \mathrm{~B}=1$, then again output $\mathrm{C}=1$. The gate must be