Show the following grammar is ambiguous

Question

I'm trying to identify a sentence that can produce more than one derivation tree. Also provide two different trees from the sentence

<S> = <A>
<A> = <A> + <A> | <B> 
<B> = a | b | c

p.s i have a hard time figuring out the sentences

Answer 1

This looks like a problem set question, so I won't give a full answer here. However, as a hint, try showing that the string a + a + a has two different parse trees.

Hope this helps!