If each side of a cuboid is doubled,its volume is
(b)becomes 4 times
(c)becomes 6 times
(d)becomes 8 times
A dictionanary says a cuboid is a rectangular parallelepiped. So it looks like any box of six rectangular faces. (A square is also a rectangular, by the way).
So the volume is length*width*height.
If all those 3 dimensions are doubled, then the original volume is doubled only according to your book?