Which of the Following Is an Example of Experimenter Bias

Which of the following is an example of experimenter bias

A)  An experimenter explicitly instructs subjects to complete tasks in a particular order, rather than allowing them to choose the order of completion. 
B)  An experimenter tries to make a favourable impression on the research subjects by being friendly and by providing a great deal of information. 
C)  An experimenter conducts her study in a completely objective manner. 
D)  An experimenter's belief in his own hypothesis affects either the subjects' behaviour or his observations of the subjects.