A linear grammar is a context-free grammar in which no production body has more than one occurrence of one variable. For example, A 0B1 or A 001 could be productions of a linear grammar, but A BB or A A0B could not. A linear language is a language that has at least one linear grammar.

The following statement is false: "The concatenation of two linear languages is a linear language." To prove it we use a counterexample: We give two linear languages L1 and L2 and show that their concatenation is not a linear language.Which of the following can serve as a counterexample?

a) L₁ ={w|w=(aaa)ⁿ(ab)ⁿ, where n is a positive integer}

L₂={w|w=(ab)ⁿ, where n is a positive integer}

b) L₁ ={w|w=aaac^n-1(ab) , where n is a positive integer}

L₂={w|w=c(aaa)ⁿ, where n is a positive integer}

c) L₁ ={w|w=aⁿbⁿ, where n is a positive integer}

L₂={w|w=(abb)ⁿ(ab)ⁿ, where n is a positive integer}

d) L₁ ={w|w=(ab)ⁿaⁿbⁿ, where n is a positive integer}

L₂={w|w=c(aaa)ⁿ(aa)ⁿ(ab) ⁿ, where n is a positive integer}

Would you plz explain me the solution?