The Main Finding of Rosenhan's Study of 8 Individuals Admitted

The main finding of Rosenhan's study of 8 individuals admitted to psychiatric hospitals is that:

A) cognitive skills change across the lifespan.
B) people who are in mental hospitals do not really have mental illnesses
C) labeling a person with a mental illness leads average people and even psychiatrists to interpret their behavior as evidence of the illness
D) There is not a single clear criteria for mental illness