Meaning: 'Root' refers to the basic part of a word from which other words can be formed.

Wrong options:

• mood: 'Mood' is a noun that refers to a temporary state of mind or feeling, which does not relate to the origin of 'tectonics.'
• mode: 'Mode' is a noun that refers to a manner or way of doing something, which does not fit the context of word origins.
• grated: 'Grated' is the past participle of 'grate,' which means to shred food into small pieces, and does not relate to the topic of word origins.

Correct answer: refers

Explanation: The verb 'refers' indicates the action of mentioning or alluding to something, which fits grammatically and contextually as it describes what the term 'plate tectonics' does.

Meaning: 'Refers' means to mention or relate to something.

Wrong options:

• mood: 'Mood' does not fit grammatically as it is a noun and does not convey the action of describing or mentioning.
• mode: 'Mode' is also a noun and does not fit the grammatical structure needed in this context.
• states: 'States' is a verb that could fit, but it does not convey the same meaning as 'refers' in this context.

Correct answer: states

Explanation: The verb 'states' is used to express a declaration or assertion, which fits grammatically and contextually as it describes what the theory of plate tectonics does.

Meaning: 'States' means to express something in spoken or written form.

Wrong options:

• mood: 'Mood' is a noun and does not fit the grammatical structure required here.
• refers: 'Refers' is a verb that does not convey the same meaning as 'states' in this context.
• fragmented: 'Fragmented' is an adjective and does not fit as it does not express an action.

Correct answer: fragmented

Explanation: The adjective 'fragmented' describes something that is broken into pieces, which fits grammatically and contextually as it describes the Earth's outermost layer.

Meaning: 'Fragmented' means broken into smaller parts or pieces.

Wrong options:

• mood: 'Mood' is a noun that does not describe the state of the Earth's outer layer.
• states: 'States' is a verb and does not fit as it does not describe the condition of the Earth's layer.
• refers: 'Refers' is a verb that does not describe the state of being broken.

Correct answer: relative

Explanation: The adjective 'relative' indicates a relationship or comparison between things, which fits grammatically and contextually as it describes how the plates move in relation to each other.

Meaning: 'Relative' means in relation to something else.

Wrong options:

• mood: 'Mood' is a noun and does not describe the nature of movement between plates.
• mode: 'Mode' is a noun that does not fit the context of describing movement.
• grated: 'Grated' is the past participle of 'grate' and does not relate to the concept of movement.