Informed consent is valid under which two circumstances?

Informed consent is a fundamental ethical and legal requirement in healthcare that ensures patients understand the procedures they will undergo. For consent to be considered valid, it is crucial that the procedure is explained in a language that the patient can understand. This ensures that the patient has a clear comprehension of what the procedure entails, including any risks, benefits, and alternatives, allowing them to make an informed decision about their healthcare.

While it's important for the patient to be awake and aware (which is related to option A), mere awareness isn't sufficient if the patient does not understand the information presented. Additionally, the physician’s comprehension of the procedure (option C) is important for effective communication, but it does not directly impact the validity of the patient's consent. Lastly, while having a witness like a nurse present when the form is signed (option D) can provide an additional layer of oversight, it doesn't guarantee that the patient understands the implications of the consent. Therefore, the emphasis remains on ensuring that the information is conveyed clearly and understandably to the patient, which makes option B the correct answer.