Question 8: Operations on Languages

8. Consider the languages L1 = Φ and L2  = {a} . Which one of the following represents L1L2*UL1* ?
(A) {∈}
(B) Φ
(C) a *
(D) {ε, a}

Ans: (A)

Explanation :
L2* = {a}* = strings of a of any length and ∈
L1L2* =  Φ {a}* = Φ [Concatenation of empty language with any language will give the empty language ]

L1* = Φ* = ∈
L1L2*UL1* = ΦU∈ = { ∈ }
So, the answer is A.

Concepts to Revise :
Languages
Operations on Languages

References :