Question
Question: Compare rotational energy barrier for the indicated bond 
A
d > c > b > a
B
a > b > c > d
C
c > d > a > b
D
b > a > d > c
Answer
d > c > b > a
Explanation
Solution
Indicated bond is a double bond maximum delocalisation (by Resonance & Hyperconjugation) maximum single bond character hence minimum rotational energy barrier.
Rotational energy barrier µ bond strength.
