Topic: Interchange of Parts of Speech,

Best Answer Explained in Below-:

The adjective form of the word 'fool' is 'foolish' (Option B). Understanding this involves recognizing the grammatical categories of words. The base word 'fool' is a noun that refers to a person who lacks good sense or judgment. To describe the quality or characteristics associated with this noun, we need an adjective, which modifies nouns and provides more information about them.

The word 'foolish' derives from 'fool' and means lacking good sense or judgment, or displaying behavior that is unwise. It conveys the qualities that might be attributed to a 'fool.'

Now, let’s consider the other options:

- A) 'befool' is a verb meaning to deceive or trick someone.
- C) 'fool' itself, while it can function as both a noun and a verb, does not serve as an adjective.
- D) 'foolishly' is an adverb, which describes the manner of an action and not a characteristic of a noun.

Hence, 'foolish' is the only option that fits as the adjective form of 'fool,' describing the quality related to the noun.