Question

Which of the following are not equivalent to expression $(a + b + c)^*$?

(A) $(a^* + b^* + c^*)^*$

(B) $\Bigl ( (ab)^* + c^* \Bigr )^*$

(C) $(a^* b^* c^*)^*$

(D) $(a^*b^* + c^*)^*$

Answer 1

Clearly b is the answer as we can see that every one is generating aaaaabbb while the second option is not generating it . The approach to this question is see in option b every a is has to be followed by b because it has (ab)*, and such restriction is not in the question.

Answer 2

B is the answer because it cannot generate b   which is generated by regular expression given in question  .

Answer 3

Answer- B  as it cannot generate single a and b while other can generate.