Which of the following isomeric heptanes can yield seven different monochlorinated products upon free radical chlorination?

n-Hexane on heating to $773 \mathrm{K}$ at $10-20$ atmospheric pressure in the presence of oxides of vanadium supported over alumina, yields

$\mathrm{n}-{\mathrm{C}}_7{\mathrm{H}}_{16}\underset{10-20\mathrm{atm}}{\overset{{\mathrm{V}}_2{\mathrm{O}}_5, 500°\mathrm{C}}{\to }}\mathrm{A}\stackrel{{\mathrm{Cl}}_2, \mathrm{h\nu }}{\to }\mathrm{B}$

What is B in the above reaction?

n-Octane when heated to $773 \mathrm{K}$ under a pressure of $10-20 \mathrm{atm}$ and in presence of a mixture of ${\mathrm{Cr}}_2{\mathrm{O}}_3, {\mathrm{V}}_2{\mathrm{O}}_5$ and ${\mathrm{Mo}}_2{\mathrm{O}}_3$ supported over ${\mathrm{Al}}_2{\mathrm{O}}_3$ as catalyst, gives