Meaning: 'Contain' means to have something within or as part of something else, indicating that these products include mercury in their formulation.

Wrong options:

• hold: The word 'hold' implies a physical grasp or support, which does not accurately describe the relationship between products and mercury in this context.
• tribute: The word 'tribute' refers to a payment or acknowledgment, which is irrelevant to the context of products containing mercury.
• require: The word 'require' suggests a necessity or need, which does not fit the context of products that include mercury.

Correct answer: measure

Explanation: The word 'measure' is the correct choice as it directly relates to the action of determining the body's temperature. It fits grammatically with the infinitive form following 'to' and contextually describes the function of thermometers accurately.

Meaning: 'Measure' means to ascertain the size, amount, or degree of something, in this case, the body's temperature.

Wrong options:

• depict: The word 'depict' means to represent or illustrate, which does not apply to the function of thermometers in this context.
• value: The word 'value' refers to the importance or worth of something, which is not relevant to the action performed by thermometers.
• detect: The word 'detect' means to discover or identify, which is not the primary function of thermometers as they specifically measure temperature.

Correct answer: changes

Explanation: The word 'changes' is the most suitable option as it refers to variations in weather conditions. It fits grammatically as a plural noun and contextually aligns with the idea of barometers indicating fluctuations in weather.

Meaning: 'Changes' refers to alterations or variations, in this case, the shifts in weather patterns that barometers can show.

Wrong options:

• contrasts: The word 'contrasts' implies a comparison between two different things, which does not fit the context of weather variations.
• marks: The word 'marks' suggests indicating or designating something, which is not the precise action performed by barometers in this context.
• contours: The word 'contours' refers to outlines or shapes, which does not accurately describe the nature of weather changes.

Correct answer: regulate

Explanation: The word 'regulate' is the correct choice as it describes the function of thermostats in controlling temperature. It fits grammatically with the subject 'thermostats' and contextually conveys the idea of maintaining a specific temperature.

Meaning: 'Regulate' means to control or maintain the rate or speed of a machine or process, in this case, the temperature of buildings.

Wrong options:

• conclude: The word 'conclude' means to bring something to an end, which does not relate to the function of thermostats.
• determine: The word 'determine' implies finding out or establishing something, which is not the primary role of thermostats as they control rather than just find out temperature.
• fold: The word 'fold' refers to bending or laying something over itself, which is irrelevant to the function of thermostats.