Choose the most appropriate word that can substitute the given group of words.

One who can't speak

Dumb

The term "dumb" can be used as an adjective to describe someone who is unable to speak. It refers to a person who lacks the ability to produce speech or communicate verbally. In the given group of words, "one who can't speak," the word "dumb" precisely captures the meaning of someone who is unable to speak.

"Bevy" refers to a large group or collection of people or things. It does not relate to the inability to speak.

"Quiet" describes a state of calmness or silence, but it doesn't specifically indicate the inability to speak.

"Orphan" refers to a child who has lost one or both parents, typically due to death. It does not represent the concept of being unable to speak.

Therefore, "Dumb" is the most appropriate word to substitute the given group of words as it directly indicates someone who is unable to speak. It's worth noting, however, that "dumb" can be considered an outdated and potentially offensive term, and "nonverbal" or "mute" are more commonly used to describe individuals who cannot speak.