Meaning: A 'solution' is an answer or explanation to a problem or question, in this case, referring to the reason behind moths' behavior.

Wrong options:

• solvent: A 'solvent' is a substance that dissolves a solute, which does not relate to the context of explaining moth behavior.
• solved: The word 'solved' is a past participle and does not function as a noun in this context, making it grammatically incorrect here.
• solute: A 'solute' is a substance that is dissolved in a solution, which is irrelevant to the explanation of moths' attraction.

Correct answer: explanation

Explanation: The term 'explanation' is appropriate as it denotes a statement that makes something clear, fitting well with the context of providing a reason for moth behavior.

Meaning: An 'explanation' is a description or account that clarifies something, in this case, the reason behind moths' attraction to light.

Wrong options:

• narration: 'Narration' refers to the act of telling a story, which does not fit the context of providing a reason or clarification.
• recipe: A 'recipe' is a set of instructions for preparing food, which is unrelated to the scientific explanation of moth behavior.
• tale: A 'tale' is a story, often fictional, and does not serve the purpose of explaining a phenomenon.

Correct answer: This

Explanation: The word 'This' is a demonstrative pronoun that refers back to the previously mentioned explanation, making it contextually and grammatically appropriate in this sentence.

Meaning: 'This' is used to indicate a specific thing or idea that is close in context, here referring to the explanation about moths' attraction.

Wrong options:

• That: 'That' is also a demonstrative pronoun but implies something more distant, which does not fit the immediate reference to the explanation.
• Those: 'Those' is a plural demonstrative pronoun, which does not agree with the singular noun 'explanation' in this context.
• Them: 'Them' is a pronoun used for objects or people, which does not grammatically fit as it does not refer back to the explanation.

Correct answer: more

Explanation: The word 'more' is an adverb that indicates a greater degree or additional quantity, fitting well in the context of questioning the necessity of navigation for moths.

Meaning: 'More' means a greater amount or degree, suggesting that there is an additional consideration regarding moth navigation.

Wrong options:

• up: 'Up' is a preposition or adverb indicating direction, which does not fit the context of the sentence about moth navigation.
• new: 'New' is an adjective that describes something recently made or introduced, which does not logically connect to the context of navigation.
• extra: 'Extra' implies something additional but does not convey the same degree of inquiry as 'more' does in this context.