4. Which statement regarding a grammar is NOT true: (a) A grammar is a system of rules to specify which combinations of an alphabet are valid (b) The syntax rules of a grammar can be represented by a finite state machine (FSM) (c) In a context-free grammar, the productions have only a single non-terminal on the left side (d) If a grammar is context-sensitive, there may be some valid strings which cannot bee recognized (e) A context-sensitive grammar has more than a single non-terminal on the left side