A patient who is to undergo surgery will be signing an informed consent. The nurse's main responsibility when informed consent is obtained isto
选项：

A: assure that patient has not rereived any sedation too to threse hours prior to signing the consent form.
B: validate that the patient understands the procedure or the treatment.
C: complete all the blank spaces in front of the patient before witnessing
D: explain the procedure and any risk factors to the patient thoroughly.