The answer is Vomiting or Nausea. After precise implantation of radon seeds for oral cancer, the nurse observes the patient for the side effects of radiation, the client may experience mucosa of the mouth and vomiting center of the brain stem, which causes the patient to experience vomiting and nauseous at times. Hematuria and Hypertension are two unaffiliated side effects of radiation therapy because they are not related to the oral cavity, while Abdominal Cramping is not expected to be one of the side effects, since the distance between the implanted radon seeds are far from the intestines.