Final answer:
Rice is the cereal least likely to result in an allergic reaction upon first feeding.
Step-by-step explanation:
Food allergies occur when the immune system reacts to substances in food as though they were harmful 'foreign invaders.' While many foods can cause allergies, according to the given information, grains are listed as one of the common foods that can trigger allergic reactions. Therefore, among the cereals mentioned, the one least likely to result in an allergic reaction upon first feeding would be rice.