Meaning: 'Factors' refers to elements or conditions that contribute to a particular result or situation, in this case, the risk of heart disease.

Wrong options:

• expenses: 'Expenses' refers to costs or financial outlays, which does not relate to health risks and is grammatically incorrect in this context.
• segments: 'Segments' implies divisions or parts of a whole, which does not fit the context of health risks associated with heart disease.
• conditions: 'Conditions' could refer to health states but does not specifically denote risk elements, making it less precise than 'factors' in this context.

Correct answer: at all

Explanation: The phrase 'at all' is used to emphasize the absence of symptoms, fitting grammatically and contextually as it conveys a complete lack of awareness regarding high blood pressure.

Meaning: 'At all' means in any way or to any extent, emphasizing that many people may not experience any symptoms of high blood pressure.

Wrong options:

• in total: 'In total' refers to the overall amount or sum, which does not convey the absence of symptoms and is grammatically incorrect in this context.
• by far: 'By far' is used to indicate a significant degree, which does not fit the context of lacking symptoms.
• by no means: 'By no means' suggests a strong denial, but it does not fit as smoothly as 'at all' in this context.

Correct answer: majority

Explanation: The word 'majority' is a noun that refers to the greater part of a group, fitting grammatically and contextually as it indicates that most people with high blood pressure do not experience symptoms.

Meaning: 'Majority' means more than half of a group, in this case, referring to most individuals with high blood pressure.

Wrong options:

• functions: 'Functions' refers to the specific activities or roles of something, which does not relate to the context of people experiencing symptoms.
• shareholders: 'Shareholders' are individuals or entities that own shares in a company, which is irrelevant to the discussion of health and symptoms.
• number: 'Number' is a general term that does not convey the idea of a group or majority, making it less suitable in this context.

Correct answer: unless

Explanation: The word 'unless' introduces a conditional clause, fitting grammatically and contextually as it indicates that symptoms would only be noticed if one takes action to check their blood pressure.

Meaning: 'Unless' means except on the condition that; it sets a condition for the occurrence of symptoms being noticed.

Wrong options:

• even though: 'Even though' introduces a contrast, which does not fit the conditional context of checking blood pressure.
• if not: 'If not' suggests an alternative condition but lacks the clarity and directness of 'unless' in this context.
• when: 'When' indicates a specific time, which does not convey the conditional aspect required in this sentence.