$3-$Methylpentane on monochlorination gives four possible products. The reaction follows free radical mechanism. The relative reactivities for replacement of $-\mathrm{H}$ are $3°:2°:1°=6:4:1...$ 

Relative amounts of $\mathrm{A}, \mathrm{B}, \mathrm{C}$ and $\mathrm{D}$ formed are:
(A)
(B)
(C)
(D)

Which configuration will be adopted by the product at carbon atoms marked ($1$) and ($2$), respectively, in the given reaction?

Consider the following reactions, which are carried out at the same temperature.

${\mathrm{CH}}_3-\mathrm{Br}+{\mathrm{OH}}^{\ominus }\stackrel{\mathrm{EtOH}}{⟶}{\mathrm{CH}}_3-\mathrm{OH}+{\mathrm{Br}}^{⊝} \left(\mathrm{i}\right)$

${\mathrm{CH}}_3-\mathrm{Br}+{\mathrm{OH}}^{\ominus }\stackrel{\mathrm{DMSO}}{⟶}{\mathrm{CH}}_3-\mathrm{OH}+{\mathrm{Br}}^{\ominus } \left(\mathrm{ii}\right)$

Which of the following statement is correct about these reactions?

Identify the major product :

Find the identity of thr compound $\mathrm{B}$ in the following reaction sequence.

$\mathrm{CH}\equiv \mathrm{CNa}+{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Br}\to \mathrm{A}$

$\mathrm{A}+{\mathrm{Cl}}_2\to \mathrm{B}$

Arrange in decreasing order of the rate of ${\mathrm{S}}_{\mathrm{N}}2$ reaction.