Which of these search engines is specifically designed to filter out duplicate results?

The correct answer is the meta search engine, as it is designed to gather results from multiple search engines and filter them for duplicates. This type of engine aggregates results from various sources, providing a more comprehensive view without redundancy. By operating as an intermediary, a meta search engine can cross-reference the results from different search engines and remove duplicates, offering users a cleaner and more efficient search experience.

In contrast, the other types of search engines have different primary functions. A keyword search engine focuses on matching user queries with web content based on keywords but does not inherently filter out duplicates; rather, it might show multiple listings from the same source. An image search engine is specifically tailored for locating images and doesn't address the duplication of overall search results. Lastly, a commercial search engine primarily emphasizes monetization and providing results based on algorithms that may or may not prioritize duplicate filtering.