Which sentence from a research paper on currently popular fitness trends (like crossfit) demonstrates how to directly quote a source (rather than how to paraphrase a source)?

a) the number of summer fitness boot camps and crossfit openings have skyrocketed in major cities since 2010.

b) crossfire owner, chris brannon claims that "our enrollment has increased by 60% in the last six months alone."

c) similar to how fad diets occasionally sweep the nation, new fitness trends have arisen and become almost omnipresent on social media.

d) while popular, not all fitness experts are with the sudden rise of extreme fitness trends that are not appropriate for everyone.