Meaning: 'Source' refers to the place or thing from which something originates or can be obtained, in this case, the origin of radiation.

Wrong options:

• snares: Snares are traps for capturing animals and do not relate to the concept of radiation; thus, it does not fit contextually or grammatically.
• sorrow: Sorrow refers to a feeling of deep distress caused by loss or disappointment, which is unrelated to the scientific context of radiation.
• safety: Safety refers to the condition of being protected from harm, which does not logically connect to the concept of radiation's origin.

Correct answer: light

Explanation: The word 'light' is the correct choice as it refers to the speed at which electromagnetic radiation travels, which is a well-known scientific fact. It fits both grammatically and contextually within the sentence.

Meaning: 'Light' in this context refers to electromagnetic radiation that is visible to the human eye, and it also represents the speed of light, which is approximately 299,792 kilometers per second.

Wrong options:

• legion: Legion refers to a large group of people or things, which does not relate to the speed of radiation and is not a scientific term in this context.
• lament: Lament means to express sorrow or regret, which is irrelevant to the topic of radiation and its speed.
• lease: Lease refers to a contractual agreement for renting property, which has no connection to the concept of light or radiation.

Correct answer: removing

Explanation: The word 'removing' is a gerund that fits grammatically as it describes the action performed by ionizing radiation. It logically completes the sentence by explaining how ionizing radiation interacts with electrons.

Meaning: 'Removing' means to take something away or eliminate it, in this case, electrons from atoms and molecules.

Wrong options:

• repairman: Repairman refers to a person who fixes things, which does not fit the context of radiation's action on electrons.
• reports: Reports are documents or statements that convey information, which is unrelated to the action of ionizing radiation.
• rename: Rename means to give a new name to something, which does not apply to the process of ionizing radiation affecting electrons.

Correct answer: travel

Explanation: The word 'travel' is a verb that correctly describes the action of radiation moving through space. It fits grammatically and contextually, as it conveys the ability of radiation to move unseen.

Meaning: 'Travel' means to move from one place to another, which in this context refers to the movement of radiation through various materials.

Wrong options:

• tension: Tension refers to the state of being stretched or strained, which does not apply to the movement of radiation.
• thumbs: Thumbs are digits on the hand and do not relate to the concept of radiation or its movement.
• towering: Towering means to be very tall or high, which does not fit the context of radiation's ability to move.

Correct answer: include

Explanation: The word 'include' is a verb that fits grammatically and contextually, indicating that air, water, and living tissue are part of the materials affected by non-ionizing radiation. It completes the sentence logically.

Meaning: 'Include' means to contain as part of a whole, indicating that air, water, and living tissue are among the materials that non-ionizing radiation does not affect.

Wrong options:

• insane: Insane refers to a state of mental illness, which is irrelevant to the context of radiation and its effects.
• irresponsible: Irresponsible describes a lack of responsibility, which does not relate to the scientific discussion of radiation.
• inspiration: Inspiration refers to a feeling of enthusiasm or creativity, which does not fit the context of materials affected by radiation.