Correct Answer - C
From given curve,
Melting point for A = `60^(@)`C
And melting point for B = `20^(@)`C
Time taken by A for fusion = (6-2) = 4min
Time taken by B for fustion = (6.5 -4) = 2.5 min
Then `(H_(A)/H_(B))` = `(6xx4xx60)/(6 xx 2.5 xx20)=24/5`