Which of the following logic gates is a universal gate?

The logic circuit shown below has the input waveforms $A$ and $B$ as shown. Pick out the correct output waveform.

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 $Z$?

Write the symbol,truth table,function,and Boolean equation for $NOT$,$AND$,and $OR$ gates.

What are analog signals and digital signals?

The given circuit shows a combination of logic gates. Identify the equivalent gate.