Which one can actually heal a patient? A: placebos B: patient's strong will to get better

In what cases, do placebos work better? A: The patient has a lot of trust in the doctor. B: The doctor really wants to help the patient. C: The placebo looks exactly like the real medicine. D: The patient doesn't believe he will get better.

According to paragraph three, what can we learn about the experiment A: 30% of the patients take placebos. B: The effect of placebo has nothing to do with the dose. C: Patients feel still better if they are given two instead of one placebo. D: Patients know they are taking placebos rather than real drugs.