Which logic gate with inputs $A$ and $B$ performs the same operation as that performed by the following circuit?

Given $A$ and $B$ are input terminals. Logic $1 = > 5 \ V$,Logic $0 = < 1 \ V$. Which logic gate operation does the above circuit perform?

Which gate is formed by the combination of gates shown below?

Identify the correct truth table of the given logical circuit.

For the logic circuit shown,the output waveform at $Y$ is

The circuit diagram shows a logic combination. Initially, for inputs $P, Q, R$ and $S$ all at state $1$, the outputs are $X=1, Y=1$ and $Z=0$. When inputs $P$ and $R$ change to state $0$ while inputs $Q$ and $S$ remain at state $1$, what are the new states of outputs $X, Y$ and $Z$?