Results of Some of the Hawthorne Studies Were Tentatively Explained

Results of some of the Hawthorne studies were tentatively explained by what has come to be know as the Hawthorne Effect,in which

A) employee performance increases because the knowledge of participating in a study.
B) employee performance depends almost entirely on how well established a work group is
C) newer employees reach optimal performance when paired with experienced employees.
D) it is almost impossible to have any effect on the productivity of a work group.