The correct answer is 1. Citation
Explanation
A citation is the most common and appropriate method to acknowledge the authorship of a document, painting, text or any other source. This is common in the case you are writing a document and you need to mention the ideas of an expert on the subject, in this cases, it is common to enclose the ideas of the external author or source in quotation marks and then include the author's last name and date of publication in parentheses, although this varies in the case you paraphrase or summarize the ideas of the authors. Besides this, it is necessary to add complete information of the source at the end of the document in the work-cited page. According to this, it is a citation the way credit is given for an author due to his/her work. So, the correct answer is 1. Citation