Answer:
Google
Explanation:
Refseek is an "academic search engine for students and researchers"; therefore, it will only show academic results.
WorldCat is a search engine for libraries worldwide - "72,000 libraries in 170 countries".
Dogpile fetches results from other search engines such as Google, Yahoo and Bing.
This would mean that Google is the most versatile for doing anything/all of the above.
