Give the IUPAC name of the first member of alkyne series.

The correct sequence of reagents for the following conversion will be

The major product of the following reaction is

The major product in the following reactions is

${\mathrm{C}}_6{\mathrm{H}}_5-\mathrm{C}\equiv \mathrm{CH}\underset{\left(\mathrm{ii}\right)\mathrm{HI}\left(1\mathrm{eq}\right)}{\overset{\left(\mathrm{i}\right)\mathrm{HCl}\left(1\mathrm{eq}\right)}{\to }}$

Which among the following depicts the correct order of acidity?

In the compound, 

$\underset{\left(\mathrm{I}\right)}{{\mathrm{CH}}_2}=\underset{\left(\mathrm{II}\right)}{\mathrm{CH}}-\mathrm{C}\underset{\left(\mathrm{III}\right)}{\equiv \mathrm{CH}}$

The most acidic hydrogen atom is

Select the structural formula of the given compound from the box.

But-1-yne.