Parts of Speech

 Knit is a verb. E.g. Knitting is a hobby for many.

Kowtow is a verb meaning to bow respectfully or obsequiously. While it can function as a noun referring to the act itself, the verb form is the primary and most common usage, making 'verb' the correct part of speech.

 Knot is a noun. E.g. He tied the knot last year.

'Jeer' primarily means to mock or ridicule someone - an action that makes it a verb. While 'jeer' can also be used as a noun (a jeering sound), its most common usage is as a verb meaning 'to jeer at'. 'Noun', 'adjective', 'adverb', and 'preposition' are incorrect as the primary part of speech.

Jealous describes a feeling or quality, which is the function of an adjective. Adjectives modify nouns by answering what kind or which one. Verbs show action, nouns name things, and adverbs modify verbs.

Jeopardy names a situation or state, which is the function of a noun. Nouns represent people, places, things, ideas, or conditions. The common phrase 'in jeopardy' shows it as a noun.

Jerk names both a sudden quick movement and a contemptible person, making it a noun. Nouns name entities, whether concrete (person) or abstract (movement/action). Verbs would show the action itself.

To jettison means to throw or drop something, which is an action. Actions are expressed by verbs. The word can be used as 'to jettison cargo' showing its verb form. Nouns would name the thing being thrown.

A jewel is a precious stone - a physical object. Physical objects are named by nouns. Nouns identify tangible things like gems, metals, or artifacts. Adjectives would describe the jewel (shiny, rare).

A jingle is a short song or sound effect - a thing that exists. Things are named by nouns. While 'to jingle' is also a verb, the word 'jingle' itself commonly refers to the noun form (a jingle = advertising song).

Judicial relates to courts, judges, or legal proceedings, serving as a descriptive term. Words that describe or qualify are adjectives. It modifies nouns like 'judicial system' or 'judicial review'. Nouns would name the court itself.

Juice is a liquid substance - a physical thing. Substances are named by nouns. Nouns identify things you can see, taste, or touch. Verbs would show action (to juice something), but the word itself names the liquid.

To jumble means to mix things together in a confused way - an action. Actions are expressed by verbs. You can say 'jumble the pieces' or 'the papers were jumbled'. Nouns would name the result (a jumble).

Jumbo is most commonly used as an adjective meaning very large (jumbo jets, jumbo shrimp). However, it can also function as a noun in informal contexts. The answer key marks it as noun, which is acceptable though less common.

Jubilant describes a feeling or state of great joy - it shows the quality or manner of someone. Descriptive words are adjectives. It modifies people (jubilant crowd) or expressions (jubilant smile). Verbs would show action.