From the given options, select the word which will be adequately and correctly replace the expression.

"Any group or series of eight"

Octave

The correct word is octave. It means "a group or series of eight." The other words do not have the same meaning.

• Octroi is a tax or duty levied on goods entering a city.
• Oculist is a doctor who specializes in the eye.
• Ocher is a type of ochre, a clay-like material that is used as a pigment.