A. 4 cm
As we know,
Volume of cylinder = πr2h
where r = base radius
h = height of cylinder
For Given Solid cylinder,
Base diameter = 2 cm
Base radius, r = 1 cm [as radius = 1/2 diameter]
Height, h = 16 cm
Volume of cylinder, V = π(1)2(16) = 16π cm3
Now,
Let the radius of sphere be r
Volume of sphere = 4/3πr3
where r = radius
Volume of 12 spheres of radius r = 12 (4/3πr3) = 16πr3
Now,
Volume of 12 spheres = volume of cylinder
[As volume remains same, when a metal body is melted and recast into another metal body]
⇒ 16πr3 = 16π
⇒ r3 = 1
⇒ r = ∛1 = 1 cm
Diameter = 2r = 2 cm
Hence, diameter of each sphere is 4 cm.