Meaning: 'Influence' means to have an effect on the character, development, or behavior of someone or something.

Wrong options:

• continuous: 'Continuous' is an adjective that describes something that is ongoing, which does not fit the context of affecting effectiveness.
• discontinuance: 'Discontinuance' refers to the act of stopping something, which is contrary to the intended meaning of affecting effectiveness.
• substituents: 'Substituents' refers to atoms or groups that replace hydrogen in a compound, which is unrelated to the context of treatment effectiveness.

Correct answer: sufferers

Explanation: The term 'sufferers' is appropriate as it refers to individuals experiencing migraines, fitting the context of the sentence. It is a noun that aligns with the subject of the study being discussed.

Meaning: 'Sufferers' means people who experience pain or distress, particularly in the context of medical conditions like migraines.

Wrong options:

• devoters: 'Devoters' refers to people who are devoted to something, which does not relate to the context of experiencing migraines.
• lovers: 'Lovers' implies a romantic or affectionate relationship, which is not relevant to the context of migraine patients.
• believers: 'Believers' suggests those who have faith in something, which does not accurately describe individuals suffering from migraines.

Correct answer: headache

Explanation: The word 'headache' is a noun that directly refers to the condition being studied, making it contextually and grammatically appropriate as it describes the first instance of migraine attacks.

Meaning: 'Headache' refers to pain in the head, which is the primary symptom being investigated in the study.

Wrong options:

• sheldrake: 'Sheldrake' is a proper noun and does not relate to the context of migraine or headaches.
• fishcake: 'Fishcake' is a food item and is irrelevant to the medical context of the sentence.
• intake: 'Intake' refers to the act of taking something in, which does not fit the context of describing a migraine attack.

Correct answer: patients

Explanation: The word 'patients' is a noun that refers to individuals receiving medical treatment, fitting the context of the study perfectly as it describes those involved in the research.

Meaning: 'Patients' means individuals who are receiving medical care or treatment.

Wrong options:

• refutations: 'Refutations' refers to disproving something, which does not fit the context of individuals receiving treatment.
• complaisance: 'Complaisance' refers to a willingness to please others, which is not relevant to the context of medical treatment.
• fixations: 'Fixations' refers to an obsessive focus on something, which does not relate to the context of patients in a medical study.

Correct answer: apparently

Explanation: The word 'apparently' is an adverb that indicates something seems to be true based on what is known, fitting the context of how patients are likely to respond to treatment based on doctors' messages.

Meaning: 'Apparently' means as far as one knows or can see, suggesting that the likelihood of response is based on perception.

Wrong options:

• deputy: 'Deputy' refers to a person appointed to assist or act in the place of another, which does not fit the context of treatment response.
• dreadfully: 'Dreadfully' is an adverb that indicates something is done in a terrible manner, which does not fit the positive context of treatment response.
• affinity: 'Affinity' refers to a natural liking for or attraction to something, which does not relate to the likelihood of responding to treatment.