Meaning: 'Contain' means to have something inside or include it as part of something.

Wrong options:

• fix: The verb 'fix' means to repair or correct something, which does not relate to the context of products having mercury.
• cover: The verb 'cover' means to place something over or upon, which does not accurately describe the relationship between products and mercury.
• constrain: The verb 'constrain' means to limit or restrict, which does not fit the context of products that include mercury.
• regulate: The verb 'regulate' means to control or maintain the rate or speed of a machine or process, which does not apply to the inclusion of mercury in products.
• show: The verb 'show' means to display or demonstrate, which does not fit the context of products containing mercury.

Correct answer: show

Explanation: The verb 'show' is appropriate here as it indicates that barometers demonstrate or indicate changes in weather. This fits grammatically and contextually, as it describes the function of barometers.

Meaning: 'Show' means to display or reveal something, in this case, changes in weather.

Wrong options:

• fix: The verb 'fix' means to repair or correct, which does not relate to the function of barometers in measuring weather changes.
• cover: The verb 'cover' means to place something over, which does not accurately describe the function of barometers.
• constrain: The verb 'constrain' means to limit or restrict, which does not fit the context of barometers showing weather changes.
• regulate: The verb 'regulate' means to control or maintain, which does not apply to the function of barometers in showing weather changes.
• contain: The verb 'contain' means to hold or include, which does not fit the context of how barometers function.

Correct answer: regulate

Explanation: The verb 'regulate' is suitable here as it describes the function of thermostats in controlling the temperature of buildings. This aligns grammatically with the plural subject 'thermostats' and fits the context of temperature management.

Meaning: 'Regulate' means to control or maintain the rate or temperature of something, in this case, buildings.

Wrong options:

• fix: The verb 'fix' means to repair or correct, which does not relate to the function of thermostats in managing temperature.
• cover: The verb 'cover' means to place something over, which does not accurately describe the function of thermostats.
• constrain: The verb 'constrain' means to limit or restrict, which does not fit the context of thermostats regulating temperature.
• contain: The verb 'contain' means to hold or include, which does not apply to the function of thermostats in controlling temperature.
• show: The verb 'show' means to display or demonstrate, which does not fit the context of thermostats managing temperature.