How Did Researcher Robert Rosenthal Construct an Experiment to Test

How did researcher Robert Rosenthal construct an experiment to test the influence of teacher expectations on student performance?

A) He chose random students who were equal in intelligence and told the teacher the students were advanced, then compared their improvement to unlabeled students.
B) Students of equal intelligence were randomly assigned to either advanced or lower level classes for a year, and their performance was compared.
C) The improvement of highly capable students from a baseline was compared to the improvement shows by students thought to have less academic capability.
D) He compared the improvement of students with highly qualified teachers to the improvement of students with first year teachers.