Automata Question: Linear and context free grammars

Hello, I have been stuck on this problem for awhile and was wondering if someone could help me out. Any help is appreciated! Please explain what you did to come to your conclusion as it would be super helpful!

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 anbn, where n is a positive integer) L2 (ww (aa) (bb) where n is a positive integer b) L (w w n-1 (ab), where n is a positive integer L2 (ww (aaa)n. where n is a positive integer o c L (wlw (aaa)n- (ab) where n is a positive integer) L2 W WRC (aaa) cad where n is a positive integer d) L (ww aaa(aba) ab), where n is a positive integer) L2 W WRC (aaa)n. where n is a positive integer