Detailed Instructions: You are given a passage. You need to construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) its answer is the whole paragraph. Avoid creating questions that can be answered correctly without actually understanding the paragraph.
Q: Definitions of fluoride on the Web:

* a binary compound of fluorine with another element; added to drinking water to help prevent tooth decay.
http://www.wef.org/publicinfo/newsroom/wastewater_glossary.jhtml

* a mineral that can be found in water and toothpaste that can help prevent tooth decay.
http://www.chw.org/display/PPF/DocID/2153/router.asp

* A chemical that helps prevent tooth decay. Fluoride may be present in drinking water or applied to the teeth.
http://www.seniormag.com/conditions/cancer/cancerglossary/f.htm

* A chemical applied to the teeth to prevent tooth decay.
http://www.austincancercenters.com/glossary.shtml

* A mineral that is effective in preventing and reversing the early signs of dental caries. Fluoride occurs naturally and contains the element fluorine.
http://science.education.nih.gov/supplements/nih2/oral-health/other/glossary.htm

* Topical application of a gel or liquid that prevents decay.
http://www.drhart.com/2003/2003_definitions.htm

* A chemical that is used to strengthen the tooth enamel. Added to many public water supplies and toothpastes. << Back to top
http://www.1800dentist.com/faq/dictionary.aspx
A:
Is fluoride a compound or just two fluorine atoms?