In which of the following complexes is the oxidation state of the metal zero?

Consider the following reactions:
$C_2H_2 \xrightarrow[500^{\circ}C]{\text{red hot iron tube}} A$
$A \xrightarrow[70^{\circ}C]{\text{conc. } HNO_3, \text{conc. } H_2SO_4} B$
$B \xrightarrow{LiAlH_4} C_6H_5-N=N-C_6H_5$
$A$ and $B$ are:

The hybridisation of $Xe$ and the number of lone pairs of electrons on it in $XeF_6$ are

Which of the following is not a polyamide?

In the electric network shown,when no current flows through the $4 \Omega$ resistor in the arm $EB$,the potential difference between the points $A$ and $D$ will be $.............\,V$.

In an experiment,four quantities $a, b, c$ and $d$ are measured with percentage errors of $1\%, 2\%, 3\%$ and $4\%$ respectively. Quantity $P$ is calculated as $P = \frac{a^3 b^2}{cd}$. The percentage error in the measurement of $P$ is .......... $\%$