"Nemesis" is a noun that refers to a long-standing rival. Of the answer choices, the word with the closest meaning is "enemy," which means rival or nemesis.  "Feud" refers to a prolonged dispute; "diagnosis" means the act of classifying a problem or illness; and a "sonnet" is a poem made up of fourteen lines.

A "recluse" is a person who lives apart from society. The best choice is "hermit" because it has the same definition as "recluse." 

Your “nemesis” is your enemy, so "enemy" is the correct answer. To provide further help, an “ally” is someone who is on your side or a friend, an “accomplice” is someone who works with you, usually on a risky or nefarious mission, “protagonist” means hero, and “antagonist” means villain. “Nemesis” is an antonym of “ally” and “accomplice.” Likewise, “protagonist” is an antonym of “antagonist.”

A “rascal” is someone prone to bad behavior, a scoundrel. To provide further help, a “contributor” is someone who helps something get done; a “politician” is someone tasked with making laws and governing; a “principle” is a guiding standard of belief or morals; “rakish” means charming and dashing. 

A "colleague" is a coworker or someone a person works with, so "coworker" is the correct answer. An "autobiography" is a book written by someone about that person's own life. "Assignment" means task or work given to a specific person. An "author" is a person who writes a story, novel, or other book. "Task" means piece of work that needs to be completed.

A "guardian" is another name for someone who looks after someone else or a protector. To help you, a "student" is someone who goes to school. 

A “captive” is someone held somewhere against their will under the control of another person or other people, so the answer choice closest in meaning to "captive" is "prisoner." A “student” is someone who attends school, and a "warden" is someone who is in charge of something, like a "prison warden" or a "park warden." Also, while something "captivating" is fascinating, it doesn't mean that "fascination" and "captive" are synonyms; they are not.

A “monarch” is a king or queen, so "queen" is the correct answer. A “representative” is someone chosen in a democracy to carry out the wishes of the people.

"Novice" derives from the Latin "novus," which means new, so it makes sense that a "novice" is someone who is new at something, or a "beginner." As for the other answer choices, an “expert” is someone who knows a lot about something and has a lot of experience; a “respondent” is someone who responds to or answers something; and a “representative” is someone who is chosen by the people who carry out their wishes, and a "librarian" is a person who works at and helps run a library.

A “peer” is a classmate, someone in your social group. "Fellow," when used as a noun, can mean someone doing the same thing as you are, so it is the answer choice closest in meaning to "peer."