The correct option is D 5:4
Given, diameters of two cones are equal.
We know that, diameter = radius2
Implies radii of the two cones are also equal
Given, the slant heights are in the ratio 5:4.
Let the slant height of 1st cone be l1 and slant height of 2nd cone be l2.
Curved surface area of the first cone =πrl1
Curved surface area of the second cone
Now, ratio of their curved surface areas
So, the ratio of curved surface areas is 5:4.