Answer:
I think it would be the third one, when you read it aloud it sounds the most natural.
Explanation:
The last choice, "Teens who sleep less than 5 hours a night suffer from more immune related illnesses according to a study released in 2015 by the American Journal of Medicine." It gives a source to where the information had been gathered.
APA in-text citation style uses the author's last name and the year of publication, for example: (Field, 2005). For direct quotations, include the page number as well, for example: (Field, 2005, p. 14) Hope this helps!