Ans. (ii) and (iii)
Explanation:
In (ii) trans pent-2-ene
The bond moments of C—CH3 and C—CH2—CH3 are not cancelled exactly due to diffence in +I effect of —CH3 and —CH2—CH3 even they are opposite.
+I for —CH2—CH3 is more than —CH3
(iii) cis hex-3-ene
The bond moments of both C—CH2—CH3 are equal but they are not opposite to each other and they are inclined to each other at an angle of 600, hence it has dipolemoment.