Which one of the following species will be most reactive in ${\mathrm{S}}_{\mathrm{N}}2$ reaction?

Determine the major product formed in the following reaction:

${\mathrm{CH}}_3\mathrm{CH}\left(\mathrm{Cl}\right){\mathrm{CH}}_2–{\mathrm{CH}}_2\mathrm{OH}\stackrel{\mathrm{aqueous} \mathrm{NaOH}}{\to }$

What is the correct order of ${\mathrm{S}}_{\mathrm{N}}1$ reactivity in the following?

Describe the following reaction.