One form of plagiarism involves a. using an author's organization or sentence structure without citation. b. referring to information that is common knowledge. c. introducing a quotation with a signal phrase. d. restating an author's ideas in your own words with a citation.

explanation: the line "to save the day, harry must get past a scary three-headed guard dog" from the summary best justifies the conclusion that harry potter and the sorcerer’s stone was influenced by ancient greek mythological literature. the three other choices had nothing to do with ancient greek literature - and the words "three-headed guard dog" are what makes that choice the correct answer.