The correct answer is A. The patient was advised by the doctor not to eat rice.
The other options are incorrect because they do not accurately reflect the tense of the sentence. Option B is in the past perfect tense, which is used to talk about something that happened before another event in the past. Option C is in the present progressive tense, which is used to talk about something that is happening now or that is happening repeatedly. Option D is in the perfect tense, which is used to talk about something that happened before a specific point in time.
In the sentence “The doctor advised the patient not to eat rice,” the doctor is giving the patient a piece of advice. The advice is not something that has already happened or is happening now, but rather something that the patient should do in the future. Therefore, the correct tense to use is the simple present tense.