Meaning: Blocking means to obstruct or hinder something from happening.

Wrong options:

• excess: 'Excess' is a noun that refers to an amount that is more than necessary, which does not fit grammatically or contextually in this sentence.
• process: 'Process' is a noun that refers to a series of actions or steps taken to achieve a particular end, which does not relate to the action of hindering research.
• glimmers: 'Glimmers' is a noun that refers to faint or brief lights, which does not fit the context of obstructing research.
• detect: 'Detect' is a verb that means to discover or identify, which does not fit the context of the sentence as it does not relate to hindering research.
• ground: 'Ground' is a noun that refers to the solid surface of the earth, which is irrelevant in this context.

Correct answer: glimmers

Explanation: The term 'glimmers' refers to faint or brief flashes of light, which fits contextually as it describes the stars in the night sky. It also aligns grammatically as a plural noun that complements the preceding phrase about stars.

Meaning: Glimmers are faint or brief lights, often used to describe stars or other small light sources.

Wrong options:

• excess: 'Excess' is a noun that does not relate to the description of stars and does not fit grammatically in this context.
• process: 'Process' is a noun that refers to a series of actions, which does not describe the nature of stars.
• blocking: 'Blocking' is a gerund that does not fit as it does not describe the stars themselves.
• detect: 'Detect' is a verb that means to discover, which does not fit as it does not describe a quality of stars.
• ground: 'Ground' is a noun that refers to the earth's surface, which is irrelevant in this context.

Correct answer: prevent

Explanation: The word 'prevent' is a verb that indicates the action of stopping something from happening. It fits grammatically as it follows 'to' and aligns contextually with the need to take action against light pollution.

Meaning: Prevent means to stop something from occurring.

Wrong options:

• excess: 'Excess' is a noun that does not fit grammatically or contextually as it does not relate to taking action against light pollution.
• obscures: 'Obscures' is a verb that means to make something difficult to see, which does not fit the context of taking proactive measures.
• blocking: 'Blocking' is a gerund that does not fit as it does not convey the action of stopping light pollution.
• detect: 'Detect' is a verb that means to discover, which does not fit in the context of taking action against light pollution.
• ground: 'Ground' is a noun that does not relate to the action of preventing light pollution.

Correct answer: detect

Explanation: The word 'detect' is a verb that means to discover or identify, which fits grammatically as it follows 'can' and aligns with the context of discussing the capabilities of the human eye.

Meaning: Detect means to discover or identify something, especially something that is not immediately obvious.

Wrong options:

• excess: 'Excess' is a noun that does not fit grammatically or contextually as it does not relate to the ability of the human eye.
• prevent: 'Prevent' is a verb that means to stop something from happening, which does not fit in the context of what the eye can do.
• blocking: 'Blocking' is a gerund that does not relate to the action of the eye and does not fit grammatically.
• glimmers: 'Glimmers' is a noun that does not fit as it does not describe an action related to the eye's capabilities.
• ground: 'Ground' is a noun that does not relate to the action of detecting stars.

Correct answer: obscures

Explanation: The word 'obscures' is a verb that means to make something difficult to see or understand. It fits grammatically as it follows the subject 'the light emitted' and aligns contextually with the discussion of how light pollution affects visibility of stars.

Meaning: Obscures means to make something unclear or difficult to see.

Wrong options:

• excess: 'Excess' is a noun that does not fit grammatically or contextually as it does not relate to the action of light affecting visibility.
• prevent: 'Prevent' is a verb that means to stop something from happening, which does not fit in the context of describing the effect of light pollution.
• blocking: 'Blocking' is a gerund that does not fit as it does not describe the action of light affecting visibility.
• detect: 'Detect' is a verb that means to discover, which does not fit in the context of how light pollution affects stars.
• ground: 'Ground' is a noun that does not relate to the action of obscuring visibility.