According to the federal regulations, which of the following studies meets the definition of research with human subjects? a researcher sets up a meeting with the superintendent of a large and diverse public school system to get data about the ethnic composition of the school system and the number of students receiving free lunches. undergraduate students in a field methods class are assigned a research question and asked to interview another classmate, to be followed by a class discussion on interview techniques. a cognitive psychologist enrolls undergraduate students for a computer-based study about the effect of mood on problem-solving behaviors. a researcher conducts a comparison of the comments made in a publicly available blog and the blogger's comments on a similar topic in a weekly magazine.

the answer is: A cognitive psychologist enrolls undergraduate students for a computer-based study about the effect of mood on problem-solving behaviors.

Here the requirement for research with human subjects according to the Fed :

"Obtains information or biospecimens through intervention or interaction with the individual, and uses, studies, or analyzes the information or biospecimens; or Obtains, uses, studies, analyzes, or generates identifiable private information or identifiable biospecimens."

The experiment on this ption fulfill the criteria because:

- The experiment should use studies or analytics to obtain some sort of private information from the subjects.  (such as their mood)

- The experiment should make some sort of intervention that can be used to measure its hypothesis. (in the case above, the researchers could put the subject under a certain level of stress before telling them to  solve a set of problems)

- The researchers need to interact with the subject in a certain way. (since the researchers meet the undergraduate directly, it's considered as an interraction)