Within the three restricted grammar classes of the Chomsky hierarchy, which is…

Concept

The Chomsky hierarchy orders restricted grammar classes by expressive power. Relaxing production restrictions enlarges the corresponding language family.

• Type 3 denotes regular grammar.

• Type 2 denotes context-free grammar.

• Type 1 denotes context-sensitive grammar.

Type 0 unrestricted grammar lies outside the three restricted classes named in the question.

Application

For the three named classes, the containment order is regular languages ⊂ context-free languages ⊂ context-sensitive languages. The final class in this containment chain is therefore the most general one in the stated comparison.

Comparison

Contrast

• Regular grammar is the narrowest listed class and is contained in the context-free class.

• Context-free grammar is more general than regular grammar but remains contained in the context-sensitive class.

• “None of the above” would apply only if no named class met the condition; the containment order identifies a named class.

Cross-check

The recognizing-machine hierarchy gives the same order: finite automata are less powerful than pushdown automata, which are less powerful than linear-bounded automata. Hence the result is context-sensitive grammar.