Tips & Tricks Let’s try filling in all the options: A. abbbb ⇒ a b aba b b ba b ab ⇒ Meaningless. B. baabb ⇒ b a aba a b ba bab ⇒ Meaningless. C. bbaba ⇒b baba a b ba a ab ⇒ meaningless. D. abbab⇒ a b aba b a ba b ab ⇒ Meaningful as it’s ‘ab’ written for 6 times.