Meaning: 'Preservative' refers to a substance that is added to food to prevent it from spoiling or to maintain its freshness.

Wrong options:

• preserving: 'Preserving' is a gerund form and does not fit as it would require a different grammatical structure, such as 'as a method of preserving.'
• preserve: 'Preserve' is a verb and does not fit grammatically as it cannot follow 'a' in this context.
• preserved: 'Preserved' is the past participle form and does not function as a noun, making it unsuitable here.

Correct answer: In addition

Explanation: The phrase 'In addition' serves as a transitional phrase that introduces an additional point, fitting well contextually as it connects the previous statement about vinegar's uses to the new information about health benefits.

Meaning: 'In addition' means 'also' or 'furthermore,' indicating that what follows adds to the previous information.

Wrong options:

• Although: 'Although' introduces a contrast, which does not fit the context of adding information about vinegar's benefits.
• Firstly: 'Firstly' implies a sequence of points, which is not appropriate here as the sentence is not listing items.
• Another: 'Another' suggests a singular additional item, which does not align with the broader context of introducing multiple health benefits.

Correct answer: have been shown

Explanation: The phrase 'have been shown' is the correct present perfect passive form, indicating that the results of the study are relevant to the present, fitting grammatically with the plural subject 'cells.'

Meaning: 'Have been shown' means that evidence or results have been demonstrated or proven in the past and are still applicable now.

Wrong options:

• has been show: 'Has been show' is incorrect due to the misuse of 'show' in its base form instead of the past participle 'shown.'
• have been shown: This option is actually correct but is repeated here for clarity; it fits the context and grammar perfectly.
• has be show: 'Has be show' is grammatically incorrect as it mixes verb forms and lacks the past participle.

Correct answer: put on

Explanation: The phrase 'put on' is a phrasal verb that means to gain weight, fitting contextually as it describes the effect of consuming cranberry weight in contrast to vinegar consumption.

Meaning: 'Put on' means to gain or increase in weight, particularly in this context referring to the volunteers' experience with cranberry consumption.

Wrong options:

• put off: 'Put off' means to delay or postpone, which does not fit the context of weight gain.
• carried off: 'Carried off' implies successfully achieving something, which does not relate to weight gain.
• got on: 'Got on' is vague and does not specifically refer to weight gain, making it unsuitable in this context.

Correct answer: power

Explanation: The word 'power' functions as a noun that describes the capacity or ability of the brain, fitting grammatically and contextually as it aligns with the discussion of cognitive functions.

Meaning: 'Power' in this context refers to the mental capacity or ability to think, reason, and remember effectively.

Wrong options:

• influence: 'Influence' refers to the capacity to have an effect on someone or something, which does not fit the context of cognitive abilities being discussed.
• thought: 'Thought' is a noun that refers to the process of thinking, but it does not convey the same sense of capacity or ability as 'power.'
• dream: 'Dream' refers to a series of thoughts or images occurring during sleep, which is unrelated to the context of cognitive function.