One Word Substitution

A fold is an enclosure for sheep. While a pen is also an enclosure, fold is the specific term associated with sheep.

 When people come over for a social gather, we say we are having or keeping "company".

A den is the specific term for the home or lair of a lion. The other options are incorrect for a lion.

A mosque is the designated place of worship for followers of Islam. Other options refer to places of worship for different religions: temple (Hinduism/Buddhism), church (Christianity), and synagogue (Judaism).

 Rabbits are kept in a hutch.

A chiropodist, also known as a podiatrist, is a healthcare professional who specializes in the care and treatment of feet and, by extension, related lower limb issues. Mammalogist studies mammals, ethologist studies animal behavior, and dentist studies teeth.

A library is a place or collection where books are kept for reading or reference. Bench, posse, and bevy are collective nouns for other things, such as judges, law enforcement, or groups of people/birds.

A sculptor is an artist who creates three-dimensional art by carving or shaping materials like stone, wood, or metal. Painters use pigments, vintners make wine, and vendors sell goods.

An oculist is an older term for an ophthalmologist or eye doctor who treats eye diseases. Allergists treat allergies, exodontists specialize in tooth extraction, and dermatologists treat skin conditions.

 An author writes books. A poet writes poetry specifically. An almoner collects alms or tithes for a church. A novelist is an author who specializes in writing novels.

 A collier is a coal miner. A jockey rides a race horse. A cutler makes knives. A tanner works with hides and animal skins to prepare leather.

A brunette is a woman with brown or dark hair. Blonde refers to light hair, and the other terms are unrelated to hair color.

 A fruitarian is one who eats only fruits. A vulgarian is one who is unrefined and vulgar. A vegetarian is one who eats who eats only fruit and vegetables and other non-meat products. A barbarian is an uncivilized person.

Oology is the branch of ornithology that deals with the study of bird eggs. Biology is the study of life, entomology is the study of insects, and zoology is the study of animals.