Answer the Question. -Double Blinding Is Used in an Experiment to Avoid Which

Answer the question.
-Double blinding is used in an experiment to avoid which of the following problems?

A) If improvement is observed in a patient, it is difficult to know whether this is due to the treatment or the placebo effect
B) If the researcher knows that the patient received the treatment, the researcher may also experience health changes
C) If the patient knows that he received the placebo and not the treatment he may be angry and fail to tell the truth
D) If an experimenter knows whether the patient has received the treatment or the placebo, this may influence how he or she questions the patient