Hemoglobin and myoglobin are both heme-containing proteins, where the heme group is responsible for oxygen binding. Hemoglobin is found in red blood cells and transports oxygen throughout the body, while myoglobin is found in muscles and stores oxygen. Both proteins have a heme core that plays a critical role in oxygen transport and storage.
Thus, the correct answer is (A) hemoglobin and myoglobin.