Ramon Is Studying Bullying Behaviour Among Elementary Schoolchildren

Ramon is studying bullying behaviour among elementary schoolchildren. He arranges to spend one day following around a class of children, making notes on their behaviour. Unfortunately, when he presents his research to his professor, his professor says that Ramon's data were compromised by the way he collected it. What did Ramon forget to do?

A) he did not introduce himself to each student; that is, he failed to build rapport with his subjects
B) he did not introduce himself to the children as a person in authority; as a result, the children may not have paid enough attention to him throughout the day
C) he forgot to take some kind of reward to thank the children for having him there
D) he did not use unobtrusive measures, and his presence may have affected the children's behaviour
E) his measures were not reliable