Researchers told grade school teachers that a small number of students were likely to be "late bloomers" during this academic year. Even though the students were actually randomly selected, the teachers' expectations were reflected in the students' performance. What is this is an illustration of

Self-fulfilling prophecy

Explanation:

A self-fulfilling prophecy is a term in sociopsychology that describes the belief or expectation of an individual predicting or expecting an outcome, and this outcome or expectation coming to pass, based on the individual's belief that it will pass and such person's resulting behaviors aligning to fulfill the belief.

In other words, it is a form of prediction that show the effects of the potential power of stereotypes and other sources of expectations on human behavior that causes itself to be true due to the behavior of the believer.

Hence, in this case, when the teachers' expectations were reflected in the students' performance, this is an illustration of SELF-FULFILLING PROPHECY.

the answer is a. monarch