Task: Question Answering
Input (English): Background Paragraph: Allergy symptoms can range from mild to severe. Mild symptoms might include itchy eyes, sneezing, and a runny nose. Severe symptoms can cause difficulty breathing, which may be life threatening. Keep in mind that it is the immune system and not the allergen that causes the allergy symptoms. Allergy symptoms can be treated with medications such as antihistamines. Severe allergic reactions may require an injection of the hormone epinephrine. These treatments lessen or counter the immune system’s response. 
Story: Robert studied two groups of patients. Group O had mild allergy symptoms, while group R displayed severe allergy symptoms. 
Question: Which group experienced more difficulty breathing?
Output (English): group R.