Answer:
The correct answer is letter "E": Population.
Step-by-step explanation:
The population is composed of all the individuals to whom may apply a certain given research. It is also called the universe. In difference with the target population, the population itself is not a certain amount of individuals but all of them.
In the case, the 800 students of Arizona State University are the target population of Professor Marlow's research but the universe or population are all the students enrolled in the very same university.