In order to properly evaluate a patient's state of mind and gain informed consent prior to surgery, a substantial period of time must be spent with the operating physician by the patient to become fully aware of the pros and cons of undergoing a surgical procedure.

A)a substantial period of time must be spent with the operating physician by the patient to become fully aware of the pros and cons of undergoing a surgical procedure

B)the operating physician and the patient must spend a substantial amount of time together, thus ensuring full awareness of the pros and cons of undergoing a surgical procedure

C)the patient must spend a substantial amount of time with his or her operating physician, thus ensuring that he or she has been made fully aware of the pros and cons of undergoing the surgical procedure

D)the operating physician must spend a substantial amount of time with the patient, thus ensuring that the patient is fully aware of the pros and cons of undergoing a surgical procedure

E)the operating physician must ensure that he or she is fully aware of the pros and cons of undergoing a surgical procedure by spending a substantial amount of time with the patient

I doubt between B and D.. Can someone explain?