A search tool that sends a query to several search engines at once and lists or displays the results according to their source is a

A metasearch engine sends one query to several search engines at once and combines or lists their results.

Google is a single search engine with its own index, not a tool that queries many engines together.

Moodle is a learning-management platform for courses, unrelated to searching.

No other choice fits because metasearch engine is the correct term.

Metasearch tools save effort by aggregating results from multiple sources.

Examples include Dogpile and older services like MetaCrawler.