Synonym (most nearly the same meaning) of ORATOR is

Concept

A synonym is a word that carries nearly the same core meaning as the target word. For vocabulary derived from Latin/Greek roots, fix the root sense first, then match the option whose definition overlaps that sense most closely.

Application

ORATOR comes from the Latin orare (‘to speak, to plead before an assembly’). An orator is therefore a public speaker — someone who delivers a formal, eloquent speech to an audience. Among the options, ‘Speaker’ denotes exactly a person who speaks to an audience, so it shares the central meaning.

Contrast

• Reader — one who reads written text; about reading, not addressing an audience by speech.

• Singer — one who produces music with the voice; melody, not spoken oratory.

• Critic — one who evaluates or judges works; analysis, not public speaking.

Only ‘Speaker’ overlaps the root sense of delivering speech to an audience, so it is the nearest synonym of ORATOR.