Explanation

(d)
2, 2-dimethyl butane is 6-carbon hydrocarbon $\left( C_{6}H_{14} \right)$
$\ \ \ \ \ \ \ \ \ \ \ \ CH_{3}$
|
$CH_{3} - C - CH_{2} - CH_{3}$
|
$\ \ \ \ \ \ \ \ \ \ \ \ CH_{3}$
Rest all are the chain isomers of pentane $\left( C_{5}H_{12} \right).$
$\ \ \ \ \ \ \ \ \ \ \ CH_{3}$
|
$H_{3}C - C - CH_{3}$
|
$\ \ \ \ \ \ \ \ \ \ \ \ CH_{3}$
2,2-dimethyl propane
(neo-pentane)
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ CH_{3}$
|
$H_{3}C - CH - CH_{2} - CH_{2}$
2- methyl butane
($iso -$pentane)
$CH_{3}CH_{2}CH_{2}CH_{2}CH_{3}$
n-pentane