As, A' + AB = 0
A' can't be 1 because if A'=1 this implies 1+AB which is not 1 therefore, A'=0 => A=1
now AB has to be 0 to satisfy the equation, therefore B has to be 0 So , A=1, B=0
Now AB=AC
as A=1, B=0 So C must be 0 then only AC will be 0. So, C=0
AB+AC'+CD=C'D
now AB=0 as B is 0 then AC'=1 (as A=1 , C'=1) , CD=0 as C is 0
So LHS is 1 now for RHS to be 1, C' and D both have to be 1 therefore D=1
So A=1, B=0, C=0, D=1
option a) is the ans.