An organic compound C_4 H_8 O[latex] , is found to be optically active. Which of the following could it be?</p>
<p style="padding-left: 40px">(a) [latex] CH _3- CH _2- CH _2- CHO
(b) CH _2- CO - CH _2- CH _3
(c) CH _2= CH - CH ( OH )- CH _3
(d) \left( CH _3\right)_2 CH - CHO