An alkane $C_7H_{16}$ is produced by the reaction of lithium di (3-pentyl) cuprate with ethyl bromide.The structural formula of the product is

Question

$\begin{array}{1 1}(a)\;\text{3-ethylpentane}&(b)\;\text{2-ethylpentane}\\(c)\;\text{3-methylhexane}&(d)\;\text{2-methylhexane}\end{array}$