Select the option which is the most appropriate one word substitution for the given group of words.

One who travels by foot

pedestrian

The most appropriate option that can be used as a one-word substitute for the given group of words is pedestrian.

• Protagonist is the main character in a story, play, or film.
• Propagandist is a person who spreads ideas or information, especially with the intention of influencing public opinion.
• Paediatrician is a doctor who specializes in the care of children.

The word pedestrian is the most appropriate because it specifically refers to someone who travels by foot. The other words do not have the same connotation of being a person who walks.