Meaning: 'Reflects' means to show or demonstrate something, in this case, how music represents our identities.

Wrong options:

• effects: 'Effects' is a noun that refers to the results of something, which does not fit grammatically as the sentence requires a verb.
• suspects: 'Suspects' is a verb that implies doubt or suspicion, which does not align with the context of music representing identity.
• respects: 'Respects' is a verb that means to admire or hold in high regard, which does not convey the intended meaning of music showing who we are.

Correct answer: leading

Explanation: The word 'leading' is an adjective that describes the researcher as someone who is at the forefront of their field, fitting grammatically and contextually as it indicates the researcher is prominent in their area of study.

Meaning: 'Leading' means being at the forefront or most important in a particular field or area.

Wrong options:

• reading: 'Reading' is a noun that refers to the act of interpreting written text, which does not fit the context of describing a researcher.
• steading: 'Steading' is not a commonly used term in this context and does not convey any relevant meaning related to a researcher.
• grading: 'Grading' is a noun that refers to the process of evaluating or scoring, which does not apply to the description of a researcher.

Correct answer: adopt

Explanation: The word 'adopt' is a verb that fits grammatically as it describes the action mothers take when they use playful voices with infants. Contextually, it aligns with the idea of mothers using a specific style of communication, making it the correct choice.

Meaning: 'Adopt' means to take on or start to use a particular style or manner, in this case, the playful voice used by mothers.

Wrong options:

• great: 'Great' is an adjective that does not fit grammatically or contextually as it does not describe an action related to mothers' voices.
• state: 'State' is a verb that means to express something clearly, which does not apply to the context of how mothers communicate with infants.
• stop: 'Stop' is a verb that means to cease an action, which contradicts the idea of mothers engaging with their children.

Correct answer: critical

Explanation: The word 'critical' is an adjective that fits grammatically as it describes the type of need that has arisen due to evolutionary changes. Contextually, it emphasizes the importance of strong relationships, making it the most appropriate choice.

Meaning: 'Critical' means extremely important or essential, particularly in the context of relationships between mothers and their newborns.

Wrong options:

• helping: 'Helping' is a gerund that does not fit grammatically as it does not describe a type of need but rather an action.
• stronger: 'Stronger' is a comparative adjective that does not fit the context of describing a type of need, as it implies a comparison rather than a description.
• logical: 'Logical' is an adjective that refers to reasoning or sound judgment, which does not convey the urgency or importance of the need described.

Correct answer: ensure

Explanation: The word 'ensure' is a verb that fits grammatically as it indicates the action of making certain that something happens. Contextually, it aligns with the idea of mothers taking steps to promote their infant's survival, making it the correct choice.

Meaning: 'Ensure' means to make certain that something will happen, in this case, the survival of an infant.

Wrong options:

• procure: 'Procure' is a verb that means to obtain something, which does not fit the context of guaranteeing survival.
• dellure: 'Dellure' is not a recognized English word and does not convey any relevant meaning in this context.
• allure: 'Allure' is a noun that refers to the quality of being attractive or charming, which does not fit the context of ensuring survival.