Q.

For any two sets A and B, A−(A−B) equals

1 B  
2 A−B  
3 A∩B  
4 Ac∩Bc  

Ans.

(3)

A-(A-B)=A∩(A∩Bc)c=A∩(Ac∪B)

=ϕ∪(A∩B)=A∩B