Meaning: In this context, 'signals' refers to the faint indicators or traces of paint that can be detected using the imaging technique.

Wrong options:

• traces: 'Traces' is a plural noun that could fit contextually but does not align with the specific terminology used in scientific imaging, which prefers 'signals.'
• illuminating: 'Illuminating' is a gerund that describes an action rather than a noun, making it grammatically incorrect in this context.
• thrilling: 'Thrilling' is an adjective that describes something exciting, which does not fit the context of detecting paint.
• determining: 'Determining' is a gerund that implies an action of finding out, which does not serve as a noun in this context.
• glowing: 'Glowing' is an adjective that describes something that emits light, which does not fit as a noun for microscopic indicators.

Correct answer: illuminating

Explanation: The term 'illuminating' is a gerund that describes the action of providing light to the sculptures. It fits grammatically as it serves as the main verb in the clause, indicating what is being done to the sculptures to reveal the paint.

Meaning: 'Illuminating' means to light up or make something visible, which is essential in the context of revealing the hidden paint on sculptures.

Wrong options:

• signals: 'Signals' is a noun that does not fit as a verb in this context, as the sentence requires an action word to describe what is done to the sculptures.
• traces: 'Traces' is a noun that does not convey an action and therefore does not fit grammatically in this context.
• thrilling: 'Thrilling' is an adjective that describes excitement and does not serve as a verb, making it inappropriate here.
• determining: 'Determining' is a gerund that implies an action of finding out, which does not fit the context of illuminating the sculptures.
• glowing: 'Glowing' is an adjective that describes something that emits light, which does not fit as a verb for the action being performed.

Correct answer: glowing

Explanation: The word 'glowing' is an adjective that describes the appearance of the pigment when illuminated. It fits grammatically as it modifies the noun 'white,' indicating the quality of the light that appears on camera.

Meaning: 'Glowing' refers to something that emits light or appears bright, which accurately describes how the pigment looks when it absorbs the red light.

Wrong options:

• signals: 'Signals' is a noun that does not fit as an adjective to describe the appearance of the pigment, making it grammatically incorrect in this context.
• traces: 'Traces' is a noun that does not serve as an adjective and cannot describe the quality of the light, thus it is not suitable here.
• illuminating: 'Illuminating' is a gerund that describes an action rather than a quality, making it inappropriate as a descriptor for the appearance of the pigment.
• determining: 'Determining' is a gerund that implies an action and does not fit as an adjective to describe the appearance of the pigment.
• thrilling: 'Thrilling' is an adjective that describes excitement and does not relate to the visual quality of the pigment.