Select the most appropriate one-word substitution for the given group of words. 

An instrument which act as a baby carriage 

Perambulator

The most appropriate one-word substitution for "an instrument which act as a baby carriage" is perambulator.

• Toycar is a small, wheeled vehicle that is used for play.
• Funambulist is a person who walks on a tightrope.
• Ambulance is a vehicle that is used to transport sick or injured people to a hospital.

The word perambulator comes from the Latin words "per," meaning "through," and "ambulare," meaning "to walk." A perambulator is a four-wheeled carriage that is used to transport babies and young children. Perambulators are often called prams or strollers in the United Kingdom and Australia.