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

He is now aware of transformational grammar. It is a system of language breakdown that distinguishes the connection between the several elements of a sentence and between the probable sentences of a linguistic and uses methods or guidelines (which are called transformations) to signify these relationships.