- Simpleness
- Simpleton
- Simplicity
- Simply
The correct answer is “simply” because an adverb is typically formed from an adjective by adding the suffix “-ly.” The adjective “simple” describes a noun (e.g., a simple solution). To describe how an action is performed—that is, to modify a verb—we use the adverb “simply” (e.g., He explained it simply). The other options are incorrect: “simpleness” is a noun meaning the state of being simple, “simpleton” is a noun referring to a foolish person, and “simplicity” is a noun meaning the quality of being easy to understand. Since the question specifically asks for the adverb form, which modifies verbs, adjectives, or other adverbs to indicate manner, time, or degree, “simply” is the only correct choice derived directly from the adjective “simple.”
