A:all strings containing 'ab' as substring
B:any no. of a's followed by any no. of b's or all strings not containing 'ba' as substring
C:all strings over a,b
Reverse(A):all strings containing 'ba' as substring
Reverse(B):any no of b's followed by any no. of a's or all strings not containing 'ab' as substring
option a:A+B=a^+b^+ which is proper subset of (a+b)* so False
option b: A+Reverse(B)={all strings containing 'ab' as substring } Union {all strings not containing 'ab' as substring} =(a+b)* True
option c: Reverse(A)+B= {all strings containing 'ba' as substring}
Union {all strings not containing 'ba' as substring}=(a+b)* True