Solution

The correct answer is (C), (A), (B), (D).

Key Points

• The Chomsky hierarchy classifies languages based on their generative grammars into four types, which differ in their expressive power.
• Regular Languages: These are the simplest type of languages and can be represented using regular expressions and finite automata. They are at the lowest level of the Chomsky hierarchy.
• Context-Free Languages: These languages are more powerful than regular languages and can be represented using context-free grammars. They can be recognized by pushdown automata.
• Context-Sensitive Languages: These languages can be represented using context-sensitive grammars. They are more powerful than context-free languages and can be recognized by linear bounded automata.
• Unrestricted Grammars: These are the most powerful and can generate any language that can be recognized by a Turing machine.

Thus the correct answer is ​(C), (A), (B), (D).

Additional Information

• The Chomsky hierarchy is a containment hierarchy of classes of formal grammars. It is named after Noam Chomsky, who first described it in 1956.
• The hierarchy is important in the fields of formal language theory, automata theory, and computational complexity theory.
• Understanding the expressive power of different types of grammars helps in the design and analysis of programming languages and compilers.