Explanation:

Correct option:2
solution:

The curved surface area (CSA) of cone = pi *r*l
Where r — radius
I — slant height
According to the question,
The curved surface area of two cones = 1 :8
The ratio of slant height of two cones = 1 : 4
Since the curved surface area of cone = pi *r*l

Let the radius and slant height of 1st cone be r1 and l1 respectively.

And the radius and slant height of 2nd cone be r2 and l2 respectively.

CSA of 1st cone = pi *r1*l1
CSA of 2nd cone = pi *r2*l2
=1/8
r1*1/r2*4=1/8
r1/r2=1/2

The ratio of the radius of the two cones is 1 : 2.