Question

A can be A-> derivable if and only if __________

(a) A-> A is actually a production

(b) A->B, B-> A exists

(c) Both (a) and (b)

(d) None of the mentioned

I have been asked this question by my school teacher while I was bunking the class.

Query is from Eliminating Unit Productions in portion Properties of Context Free Languages of Automata Theory

Answer 1

Right option is (a) A-> A is actually a production

For explanation: The format says: If A->B is a production, B is called A-derivable.Thus A to be A-derivable, a production : A-> A need to exist.