Answer:
Test her suspicion by checking to see whether other cats also make her sneeze, is the right answer.
Step-by-step explanation:
Since Ava is unsure about the allergic source ( Cat ) so in this case, she must check her self whether the other cats make her sneeze or not. If she finds that other cats also make her sneeze then she must avoid contact with cats and take precautionary measures prescribed by the doctor. However, if she does not find that other cats are making her sneeze then she must avoid going her best friend home because there might be other things that make her sneeze. Therefore, the first thing for Ava is to check her self and find the allergy source