"There Are Many Assets to Using a Field Study," Said

"There are many assets to using a field study," said the graduate student."First, you're dealing with correlation, so you can draw conclusions about the direction of causality.Second, you have a high degree of control over confounding variables.Third, because you're dealing with a contrived situation, you're bound to have poor external validity.And fourth, your presence might influence the subjects' behavior." Which part of the graduate student's thinking was accurate?

A) that because it's a correlational study, one can draw conclusions about causality
B) that this type of study affords a high degree of control over confounding variables
C) that because this type of study is contrived, it will result in poor external validity
D) that the experimenters' presence can influence the subjects' behavior