Answer:A. route of exposure
Explanation:Route of exposure refers to how someone got exposed to that allergen that got them sick. There are different routes of exposure , the way in which a substance enter one's body , it can be through inhalation, ingestion , skin absorption and injection. For example inhalation occurs mostly when a substance is a chemical in the form of vapours , gases , particulates and mist .
For this reason by knowing how it entered the body the pediatrician can determine what the substance might have been.