One Word Substitution

A rookery is the collective noun for a colony of rooks, which are birds related to crows. The other terms do not refer to a group of rooks.

 A menagerie is a collection of wild animals placed on display.

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.

An angler is a person who fishes with a rod and line. An archer uses a bow, a plotter creates maps or plans, and an astrologer studies celestial bodies.

A misogamist is someone who hates the institution of marriage. A misanthropist hates humanity, a chauvinist shows aggressive patriotism or prejudice, and a misogynist hates women.

A betrothed person is one who is formally engaged to be married. Spinsterhood, adulthood, and bachelorhood describe states of being, not the act of being engaged.

Mathematics is the field of study concerned with numbers, quantity, structure, space, and change. Economics, civics, and physics are distinct academic disciplines.

Sororicide is the act of killing one's sister. Suicide is killing oneself, patricide is killing one's father, and homicide is the killing of any human being.

Regicide is the act of killing a king. Fratricide is killing a brother, matricide is killing a mother, and parricide is killing a parent or close relative.

 A furrier is someone who works with furs. A glazier works with glass. A masseur is a man who provides massages for a living.. An astronomer studies the stars.

A cartographer is a person who draws or produces maps. Geologists study the earth, florists work with flowers, and usurers lend money at high interest.