The correct energy profile diagram for the above reactions is

Concept:

• Diels-Alder reaction is a type of pericyclic reaction between an alkene (called dienophile) and a diene. 
• The reaction proceeds through concerted mechanism.
• It is a syn cycloaddition reaction and thus 'locked 'cis isomer favors the reactivity with dienophile.

Explanation:

Out of A and B, Compound A is less stable and more reactive. The higher reactivity towards the dienophile can be explained by following reason

• Compound A has smaller ring and thus it acts as more rigid cis diene. While compound B is 7-membered aromatic ring. Bigger rings are more flexible. Therefore, compound B will have lower reactivity towards the dienophile.

Compound A is reactive, the activation energy will be lower for the formation of P_A.

Conclusion:

Therefore, the correct energy profile of given reactions is: