Question

18.
There are four boxes and four balls each
of colours Red, Blue, Green and White.
Each ball is put in a box such that no box
has a ball of its colour. The minimum
number of boxes to be opened such that
we can identify which coloured ball is in
which coloured box, is
(1) 1
(2) 2
(3) 3
(4) 4​

Answer 1

each ball have put in a box her identy was 4