B. volume of cylinder will remain unchanged

C. volume of the cylinder will be halved

D. volume of cylinder will be of the original volume

we know that,

The volume of cylinder having base radius = r

And original height of cylinder = h

Volume of cylinder (v) = π × r² × h

New height H = h and

New radius R = 2r (new radius = 2 times of original radius)

New volume of cylinder(V) = π × 4r² × h = πr²h = v

Hence, the volume of new cylinder = the volume of original cylinder.

And the answer is (b).