A 37-year-old patient was delivered to a hospital in unconscious state. He got a closed abdominal injury. He is suspected to have internal hemorrhage, intraabdominal injury. He is being prepared an emergency operation. By means of standard sera a physician determined his blood group and got the following results: 0(I) - no agglutination, A(II) - no agglutination, B(III) - no agglutination. What is the patient's blood group?