It is exclamation point because for example, the person who is staying this sentence probably was astonished, or find it interesting so he/she said this sentence.
Thinking about what they are saying.
Answer:
After a sentence or sentences containing information from a source or at the end if all the information comes from one source
Explanation:
In-text citation has to do with referencing, paraphrasing, or directly quoting an author or a source in a piece of writing.
This is done to avoid plagiarism and to duly give credit to a source, and this information can be represented by using the last name of the author, followed by the year of publication (APA style), for example, (Mary, 2001).