One Word Substitution

A pug is a breed of dog characterized by a physically distinctive features including a flat face and a short, wrinkled muzzle.

An optimist is a person who tends to be hopeful and confident about the future or the success of something.

A stable is a building where livestock, especially horses, are kept. In the context of breeding and training for races, stable is the best fit among the choices provided.

A restaurant is a place where people pay to sit and eat meals that are prepared and served on the premises.

A fable is a short story, typically with animals as characters, conveying a moral. An allegory is a broader narrative form.

Fossils are the preserved remains or traces of organisms from a past geological age. The other options are too informal or inaccurate.

A passport is an official document issued by a government, certifying the holder's identity and citizenship and entitling them to travel under its protection.

A literate person is one who is able to read and write. Erudite refers to having great knowledge.

An astronaut is a person who is trained to travel in a spacecraft. Cosmonaut is the term used primarily by the Russian space agency.

An epidemic is a widespread occurrence of an infectious disease in a community at a particular time. A pandemic is global.

An illiterate person is one who is unable to read or write. Uneducated is broader and may not imply the inability to read or write.

An oligarchy is a small group of people having control of a country, organization, or institution.

Effluents are liquid waste or sewage discharged into a river or the sea.

An encyclopedia is a book or set of books giving information on many subjects or on many aspects of one subject, typically arranged alphabetically.