Meaning: 'Application' refers to the act of putting something to a specific use, in this case, the genetic test for various types of PD.

Wrong options:

• adoption: 'Adoption' implies taking up or starting to use something, which does not fit the context of describing the uses of the test.
• function: 'Function' refers to the specific role or activity of something, but it does not convey the broader scope of use that 'application' does.
• operation: 'Operation' suggests a process or method of working, which is too narrow and does not capture the comprehensive use of the test as indicated in the sentence.

Correct answer: while

Explanation: 'While' is used here to indicate a contrast between two situations, which is essential for the sentence's meaning. It connects the two clauses effectively, showing the difference in alpha-synuclein levels between people with and without PD.

Meaning: 'While' means 'at the same time as' or 'whereas,' highlighting the contrast between the two groups being discussed.

Wrong options:

• when: 'When' indicates a time-related condition, which does not fit the contrasting nature of the information presented.
• where: 'Where' refers to a location, which is irrelevant in this context as the sentence is comparing conditions rather than places.
• which: 'Which' is used to introduce a clause providing additional information, but it does not serve the purpose of contrasting the two groups effectively.

Correct answer: diagnosed

Explanation: 'Diagnosed' is the correct past participle form used here to indicate that patients have been identified as having a condition. It fits grammatically and contextually as it aligns with the passive construction of the sentence.

Meaning: 'Diagnosed' means that a medical professional has determined that a patient has a specific disease or condition.

Wrong options:

• having diagnosed: This phrase is grammatically incorrect in this context as it suggests an ongoing action rather than a completed one.
• diagnosing: 'Diagnosing' is a gerund that implies the action is currently happening, which does not fit the context of discussing patients already identified.
• have been diagnosed: This option is in the present perfect tense, which is not appropriate here as the sentence requires a simple past form to maintain consistency.

Correct answer: distinguish

Explanation: 'Distinguish' is the correct verb that means to recognize or point out differences. It fits grammatically and contextually as it aligns with the intent of the sentence to differentiate between responsive and non-responsive patients.

Meaning: 'Distinguish' means to identify differences between two or more things.

Wrong options:

• determine: 'Determine' implies finding out or establishing something, which does not specifically convey the idea of recognizing differences.
• discriminate: 'Discriminate' can mean to differentiate, but it often carries a negative connotation related to unfair treatment, making it unsuitable in this context.
• recognize: 'Recognize' means to identify something as already known, which does not convey the active process of differentiating that 'distinguish' does.

Correct answer: effectiveness

Explanation: 'Effectiveness' is the correct noun that refers to the degree to which something is successful in producing a desired result. It fits grammatically and contextually as it aligns with the aim of the study being discussed.

Meaning: 'Effectiveness' refers to how well a test achieves its intended purpose.

Wrong options:

• efficiency: 'Efficiency' relates to achieving maximum productivity with minimum wasted effort, which does not directly address the success of the test in achieving its goals.
• usefulness: 'Usefulness' indicates the quality of being helpful, but it lacks the specific focus on achieving desired outcomes that 'effectiveness' provides.
• efficacy: 'Efficacy' refers to the ability to produce a desired effect under ideal conditions, which is slightly different from the broader context of 'effectiveness' in real-world applications.

Correct answer: progression

Explanation: 'Progression' is the correct noun that refers to the process of developing or moving gradually towards a more advanced state. It fits grammatically and contextually as it aligns with the discussion of the disease's development.

Meaning: 'Progression' means the process of something advancing or developing over time.

Wrong options:

• procedures: 'Procedures' refer to established methods or processes, which do not relate to the development of a disease.
• progress: 'Progress' is a noun that indicates forward movement, but it does not specifically capture the ongoing nature of disease development as 'progression' does.
• process: 'Process' refers to a series of actions or steps taken to achieve a particular end, which is too general and does not convey the specific idea of disease advancement.