NIELIT 2016 MAR Scientist B - Section C: 24

Question

Which of the following regular expressions denotes a language comprising all possible strings over the alphabet $\{a,b\}$?

• A. $a^*b^*$
• B. $(a\mid b)^*$
• C. $(ab)^+$
• D. $(a\mid b^*)$

Comments

B is the correct answer.

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B is correct

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B is the correct one

Answer 1

(A) does not generate strings like $bbabab,bababa,baaab$ etc. which are also possible strings of the given alphabet

(B)- is the answer, it generates all possible strings over the given alphabet.

(C)-does not generate epsilon.

(D)-does not generate strings like $aa,aaaa,aabb$  etc. which are also possible strings of the given alphabet.

Answer 2

As we look for the options we can easily guess that the answer will be all combinations of a and b hence the answer is (a|b)*