Why alkynes are slightly more soluble in water than alkenes and alkanes ?

Which among the following depicts the correct order of acidity?

The major product of the following reaction is

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

In the following reaction sequence



X and Y are, respectively

In the reaction


$\mathrm{x}$ and $\mathrm{y}$ , respectively, are

The correct sequence of reagents for the following conversion will be