Meaning: Regular means occurring at fixed intervals or consistently, suggesting that exercise should be a part of one's daily habits.

Wrong options:

• frequent: Frequent implies occurrence often but does not convey the sense of a structured routine as 'regular' does.
• recurrent: Recurrent suggests something that happens repeatedly but lacks the connotation of a consistent practice in daily life.
• periodic: Periodic indicates something that happens at intervals but does not imply the necessity of regularity in daily routines.

Correct answer: electric

Explanation: The term 'electric' is an adjective that correctly describes the type of can openers being referred to, fitting grammatically and contextually in the sentence.

Meaning: Electric refers to devices powered by electricity, indicating that these can openers operate using electrical energy.

Wrong options:

• electrician: Electrician is a noun referring to a person who works with electrical systems, which does not fit the context of describing can openers.
• electrically: Electrically is an adverb and does not grammatically fit as it would need to modify a verb, not a noun like 'can openers.'
• electricity: Electricity is a noun and does not serve as a descriptor for can openers, making it grammatically incorrect in this context.

Correct answer: demanding

Explanation: The word 'demanding' fits well as it describes the level of physical effort required, aligning with the context of physical activity and exercise.

Meaning: Demanding means requiring a lot of effort or energy, indicating that physical activity can be challenging.

Wrong options:

• severe: Severe implies something harsh or intense but does not accurately describe the nature of physical activity in this context.
• relaxing: Relaxing suggests ease and comfort, which contradicts the idea of physical activity being challenging or requiring effort.
• insistent: Insistent implies a strong demand or pressure, which does not fit the context of describing physical activity.

Correct answer: much

Explanation: The word 'much' is used correctly here to quantify fat in a negative context, fitting grammatically and contextually with the sentence structure.

Meaning: Much refers to a large amount of something, indicating that excess fat is a concern for health.

Wrong options:

• many: Many is used for countable nouns, while 'fat' is uncountable in this context, making it grammatically incorrect.
• little: Little implies a small amount, which contradicts the context of needing to address excess fat.
• less: Less is comparative and does not fit the context of indicating a large quantity of fat.

Correct answer: main

Explanation: The word 'main' is appropriate as it indicates the primary or most important ways to increase calorie expenditure, fitting well within the context of the sentence.

Meaning: Main means the most important or primary, suggesting that these are the key methods to achieve the goal of increasing calorie expenditure.

Wrong options:

• odd: Odd implies something unusual or strange, which does not fit the context of describing standard methods for exercise.
• large: Large refers to size and does not appropriately describe the nature of the ways to increase calorie expenditure.
• substantial: Substantial suggests a significant amount but does not convey the idea of primary importance as effectively as 'main' does.