I would say D, because it is the only answer choice that describes it as a reputable source
Fluid is a is just another word for liquid. For example water, power aid, cool aid, etc.
<span> D) declared that "separate but equal" facilities for based on race are inherently unconstitutional</span>
He was a trojan hero son of aphrodite
Sources are used in a paper to show what ideas inspired you and whose theories you would be using and you cite the sources in order to avoid plagiarism. If you don't have sources, your paper will not be valid and you could get accused of plagiarism. The more sources you use the better but you should keep in mind that they need to be important for the paper and used with a purpose and not just to increase the number of sources.