Explanation

(d)
The number of isomeric alkenes with molecular formula $C_{6}H_{12}$are 13.
(1) $CH_{2} = CH - CH_{2} - CH_{2} - CH_{2} - CH_{3}$
(2) $CH_{3} - CH = CH - CH_{2} - CH_{2} - CH_{3}$
($cis\ and\ trans\ )\$
(3) $CH_{3} - CH_{2} - CH = CH - CH_{2} - CH_{3}$
($cis\ and\ trans\ )\$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ CH_{3}$
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(4)$CH_{2} = CH - CH - CH_{2} - CH_{3}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ CH_{3}$
|
(5)$CH_{2} = C - CH_{2} - CH_{2} - CH_{3}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ CH_{3}$
|
(6)$CH_{2} = CH - CH_{2} - CH - CH_{3}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ CH_{3}$
|
(7)$CH_{3} - CH = CH - CH - CH_{3}$
($cis\ and\ trans\ )\$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ CH_{3}$
|
(8) $CH_{3} - C = CH - CH_{2} - CH_{3}$
$CH_{3}$
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(9)$CH_{3} - CH = C - CH_{2} - CH_{3}$
$\ \ \ \ (cis\ and\ trans\ )$