Meaning: 'Clue' refers to a piece of information or a hint that helps to understand something, often used in contexts where knowledge is incomplete.

Wrong options:

• dew: Dew refers to moisture that forms on surfaces, which is unrelated to understanding language.
• claw: Claw is a part of an animal's anatomy, not relevant in this context of language comprehension.
• due: Due typically indicates something that is owed or expected, which does not fit the context of lacking understanding.

Correct answer: even though

Explanation: The phrase 'even though' introduces a contrast, indicating that despite not understanding the language, listening is still important. This aligns with the overall message of the sentence about the value of exposure.

Meaning: 'Even though' is a conjunction used to express a contrast or concession, meaning 'despite the fact that.'

Wrong options:

• but also: 'But also' is a conjunction that adds information rather than contrasting it, making it unsuitable here.
• all together: 'All together' implies a collective action or state, which does not convey the intended contrast in this context.
• if so: 'If so' suggests a conditional situation, which does not fit the context of contrasting understanding with the act of listening.

Correct answer: up

Explanation: The word 'up' is used in the phrase 'make up the words,' which is a common collocation in English. It indicates the formation or composition of words, fitting grammatically and contextually.

Meaning: 'Up' in this context means to form or constitute, as in the sounds that create words.

Wrong options:

• down: 'Down' does not fit the context of forming words and is not a common collocation in this usage.
• of: 'Of' is a preposition that does not convey the action of forming or creating words, making it grammatically incorrect here.
• on: 'On' does not fit the context of word formation and does not work with the phrase structure.

Correct answer: boost

Explanation: The word 'boost' is a verb that means to increase or enhance. It fits well in the context of improving one's ability to learn a language, aligning with the overall message of the sentence.

Meaning: 'Boost' means to increase or improve something, particularly in terms of ability or performance.

Wrong options:

• evaluate: 'Evaluate' means to assess or judge, which does not fit the context of enhancing language learning.
• exaggerate: 'Exaggerate' means to overstate or make something seem greater than it is, which is not relevant to the context of learning a language.
• describe: 'Describe' means to explain or detail something, which does not convey the idea of increasing ability.

Correct answer: required

Explanation: The word 'required' is an adjective that indicates something that is necessary. It fits grammatically as it describes the structures in the brain that are essential for learning words, aligning with the context of the sentence.

Meaning: 'Required' means necessary or essential, indicating that certain structures must be in place to facilitate language learning.

Wrong options:

• requiring: 'Requiring' is a gerund that does not fit grammatically in this context, as it does not describe the structures directly.
• directed: 'Directed' implies guidance or control, which does not convey the necessary condition for learning words.
• to require: 'To require' is an infinitive form that does not fit the sentence structure, which needs an adjective to describe the brain structures.