a
\(C{H_3} - C{H_2} - \mathop {\mathop {\mathop {\mathop C\limits^| }\limits_| {\mkern 1mu} - C{H_2}}\limits^{C{H_3}\,\,\,\,\,\,\;\;\;\;} }\limits_{OH\,\,\,\,\,\;\;\;\;\;\;} {\mkern 1mu} - C{H_3}\) \(\xrightarrow{{{H^ + }}}\) \(C{H_3} - C{H_2} - \mathop {\mathop {{\text{ }}C}\limits_ \oplus ^| - C{H_2}}\limits^{C{H_{3\,\,\,\,\,\,}}\;\;\;\;{\kern 1pt} } - C{H_3}\)
The more stable carbocation is generated thus more easily it will be dehydrated.