Meaning: 'According' means 'as stated by' or 'in agreement with,' indicating that the following information is based on the referenced study.

Wrong options:

• groping: 'Groping' refers to searching blindly or feeling around, which does not fit the context of referencing a study.
• guffawing: 'Guffawing' means laughing loudly, which is unrelated to the context of providing information from a study.
• consoling: 'Consoling' means providing comfort, which does not relate to the act of referencing or stating information.

Correct answer: methylation

Explanation: The term 'methylation' is the correct scientific term that describes the process of adding methyl groups to DNA, which is relevant to the context of the study discussing age-related changes in DNA. It fits grammatically and contextually as it directly relates to the topic of the passage.

Meaning: 'Methylation' refers to a biochemical process where methyl groups are added to DNA, influencing gene activity and is crucial in understanding age-related changes.

Wrong options:

• affirmation: 'Affirmation' means confirmation or validation, which does not relate to the biochemical process discussed in the passage.
• purification: 'Purification' refers to the process of removing impurities, which is not relevant to the context of DNA changes with age.
• mortification: 'Mortification' means a feeling of shame or humiliation, which is unrelated to the scientific context of the passage.

Correct answer: researchers

Explanation: The word 'researchers' is the appropriate term to describe the individuals conducting the study, fitting grammatically as a noun that refers to people who investigate scientific questions. It aligns with the context of the passage discussing a scientific study.

Meaning: 'Researchers' are individuals who conduct studies or investigations to gain new knowledge, particularly in scientific fields.

Wrong options:

• priestesses: 'Priestesses' refers to female religious leaders, which is irrelevant to the context of scientific research.
• weaknesses: 'Weaknesses' refers to flaws or shortcomings, which does not fit the context of individuals conducting a study.
• inveiglers: 'Inveiglers' refers to those who entice or lure someone into a course of action, which is not relevant to the context of scientific research.

Correct answer: correlated

Explanation: The term 'correlated' is the correct choice as it indicates a relationship between the amount of methylation and the ages of the participants. It fits grammatically as a verb that describes how two variables are related, aligning with the context of the findings of the study.

Meaning: 'Correlated' means that there is a mutual relationship or connection between two things, in this case, methylation and age.

Wrong options:

• instantiated: 'Instantiated' means to represent or provide an example of something, which does not fit the context of measuring relationships between variables.
• hatred: 'Hatred' refers to an intense dislike, which is completely unrelated to the scientific context of the study.
• undomesticated: 'Undomesticated' refers to wild or untamed, which does not apply to the context of scientific findings.

Correct answer: scientists

Explanation: The word 'scientists' is the correct term to describe the individuals who conduct scientific research. It fits grammatically as a noun that refers to professionals in the field of science, aligning with the context of the passage discussing a study.

Meaning: 'Scientists' are individuals who study or practice science, conducting experiments and research to expand knowledge.

Wrong options:

• ripeness: 'Ripeness' refers to the state of being fully developed or matured, which does not fit the context of individuals conducting research.
• irises: 'Irises' refers to a part of the eye or a type of flower, which is irrelevant to the context of scientific research.
• iodise: 'Iodise' means to treat with iodine, which does not relate to the context of scientific study.

Correct answer: strongest

Explanation: The word 'strongest' is the correct choice as it describes the genes with the most significant correlation to age. It fits grammatically as a superlative adjective that indicates the highest degree of correlation, aligning with the context of the findings of the study.

Meaning: 'Strongest' means having the greatest strength or intensity, in this case, referring to the genes that show the most significant relationship with age.

Wrong options:

• foreshortened: 'Foreshortened' means to shorten or reduce in length, which does not fit the context of describing correlation strength.
• weakest: 'Weakest' is the opposite of strongest, indicating the least correlation, which contradicts the context of the findings.
• noticed: 'Noticed' means to become aware of something, which does not fit the context of describing the degree of correlation.