Which option best defines purifier?

• A. A device that removes dirt or harmful substances
• B. A device that stores purified water
• C. A device that filters air
• D. A device that measures energy usage

Answer: (A)

Purification means taking something that may be dirty or unsafe and removing contaminants to make it clean and safe. A purifier is a device designed to do exactly that—remove dirt or harmful substances from the substance it treats, whether water, air, or another material. This broad definition is why it’s the best choice: it describes the action of cleaning out contaminants, not just a storage function or a specific narrower task. For example, a water purifier removes microbes and chemicals from drinking water, and an air purifier removes dust and smoke from the air. In contrast, storing purified water is about containment, not cleaning, and measuring energy usage has nothing to do with purification.