John Has Just Developed the Ability to Convert a Declarative

Multiple Choice

John has just developed the ability to convert a declarative sentence (e.g., "I like pizza") into both a question (e.g., "Do I like eating pizza?") and an imperative (e.g., "I must eat pizza!") . This would indicate that he now is aware of

A) overregulation.
B) functional grammar.
C) overextension.
D) transformational grammar.