Multiple choice

Consider the languages L1 = and L2 = {a}. Which one of the following represents L1 L2* U L1*

  1. {ε}

  2. {∅}

  3. a*

  4. {ε,a}

  5. L1 L2* U L1* Result of L1 L2* is [Tex]\phi[/Tex]. {[Tex]\phi[/Tex]} indicates an empty language. Concatenation of [Tex]\phi[/Tex] with any other language is [Tex]\phi[/Tex]. It works as 0 in multiplication. L1* = [Tex]\phi[/Tex]* which is {[Tex]\epsilon[/Tex]}. Union of [Tex]\phi[/Tex] and {[Tex]\epsilon[/Tex]} is {[Tex]\epsilon[/Tex]}

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A Correct answer
Explanation

L1 is the empty set (phi). L1* is {epsilon}. L1 L2* is phi. The union of phi and {epsilon} is {epsilon}.