Perlon is

In which reaction is a racemic mixture not obtained?

In the following sequence of reactions
$CH_3CH_2OH$ $\xrightarrow{P + I_2} A$ $\xrightarrow{Mg, \text{Ether}} B$ $\xrightarrow{HCHO} C$ $\xrightarrow{H_2O} D$
then compound $D$ is -

Which of the following is the strongest conjugate base?

When two sound sources of the same amplitude but of slightly different frequencies $v_1$ and $v_2$ are sounded simultaneously,the sound one hears has a frequency equal to

The solution of $x \frac{dy}{dx} = y + x e^{y/x}$ with $y(1) = 0$ is