Meaning: 'Axis' means the central line around which something rotates, specifically in this context, it refers to Earth's rotational axis.

Wrong options:

• sundial: 'Sundial' refers to a device that tells the time based on the position of the sun, which does not relate to the concept of rotation.
• core: 'Core' refers to the innermost part of the Earth, which is not relevant to the rotation of the planet.
• surface: 'Surface' refers to the outermost layer of the Earth, but it does not accurately describe the line around which the Earth rotates.

Correct answer: dictated

Explanation: The word 'dictated' fits well as it indicates that the time is controlled or determined by Coordinated Universal Time (UTC), aligning grammatically and contextually with the sentence.

Meaning: 'Dictated' means to control or determine something, in this case, how time is set based on UTC.

Wrong options:

• delegated: 'Delegated' means assigned to someone else, which does not fit the context of time being controlled by UTC.
• addicted: 'Addicted' refers to a dependency on something, which is not relevant to the concept of time regulation.
• rotated: 'Rotated' refers to turning around an axis, which does not convey the idea of time being set or controlled.

Correct answer: dependent

Explanation: The word 'dependent' is appropriate as it indicates that astronomical time relies on the duration of Earth's rotation, fitting both grammatically and contextually.

Meaning: 'Dependent' means relying on or being influenced by something, in this case, the time based on Earth's rotation.

Wrong options:

• focused: 'Focused' means concentrated on something, which does not accurately describe the relationship between time and Earth's rotation.
• born: 'Born' refers to being brought into existence, which is not relevant to the concept of time measurement.
• available: 'Available' means accessible or ready for use, which does not convey the idea of time being reliant on Earth's rotation.

Correct answer: who

Explanation: The word 'who' is the correct choice as it serves as a pronoun referring to people, fitting grammatically and contextually in the sentence about those observing Earth's rotation.

Meaning: 'Who' is a pronoun used to refer to people, in this case, those who watch the Earth's rotation.

Wrong options:

• when: 'When' is a conjunction or adverb indicating time, which does not fit as a subject in this context.
• whose: 'Whose' is a possessive pronoun, which does not correctly refer to the subject of the sentence.
• whom: 'Whom' is an object pronoun, which is not appropriate as the subject in this context.