Topic: Interchange of Parts of Speech,

Best Answer Explained in Below-:

The term "friend" is a noun that refers to a person with whom one has a bond of mutual affection, typically one that is not based on family or romantic relationships. To transform this noun into an adjective, we use the word "friendly."

"Friendly" describes someone who acts like a friend or exhibits qualities associated with friendship, such as kindness, warmth, and helpfulness. This makes it a fitting adjective derived from the root word "friend."

Looking at the other options, "befriend" is a verb that means to become friends with someone, which does not fulfill the requirement of providing an adjective. "Friendfull" is not a recognized word in standard English; while it may appear to make sense linguistically, it lacks legitimacy in formal or colloquial usage. Lastly, "none" implies that there are no correct answers, which is incorrect since "friendly" is an established term used to describe the attributes associated with friendship.

In summary, "friendly" is the only appropriate adjective that describes or relates to a friend, making it the correct choice.