Meaning: To 'witness' means to see or experience something, particularly an event or occurrence.

Wrong options:

• show: The verb 'show' does not fit grammatically as it implies presenting something rather than observing it.
• while: The word 'while' is a conjunction that does not serve as a verb in this context and does not convey the intended action of observing.
• smooth: The word 'smooth' is an adjective and does not fit as a verb in this sentence.
• faint: The word 'faint' is an adjective that describes light, not an action, and therefore does not fit here.
• bright: The word 'bright' is also an adjective and does not convey the action of observing.

Correct answer: smooth

Explanation: The term 'smooth' is an adjective that describes the surface of the mirror, indicating it must be free of imperfections to effectively collect and focus light. This fits grammatically and contextually within the sentence.

Meaning: 'Smooth' refers to a surface that is even and free from roughness or irregularities.

Wrong options:

• show: The word 'show' is a verb and does not describe a quality of the mirror's surface, making it grammatically incorrect here.
• witness: The word 'witness' is a verb and does not function as an adjective to describe the surface, thus it does not fit.
• faint: The word 'faint' is an adjective that describes light, not a surface quality, and therefore is not appropriate here.
• bright: The word 'bright' is an adjective that describes intensity of light, not the smoothness of a surface, making it unsuitable.

Correct answer: faint

Explanation: The word 'faint' is an adjective that describes the light coming from distant galaxies, indicating it is weak or dim. This fits grammatically and contextually as it describes the type of light the mirror must collect.

Meaning: 'Faint' refers to something that is not strong or clear, in this case, the light from faraway galaxies.

Wrong options:

• show: The word 'show' is a verb and does not describe the quality of light, making it grammatically incorrect in this context.
• smooth: The word 'smooth' is an adjective that describes a surface, not light, and therefore does not fit here.
• witness: The word 'witness' is a verb and does not describe light, making it inappropriate for this blank.
• bright: The word 'bright' is an adjective that describes strong light, which contradicts the context of the light being faint.