Task: Question Answering
Input (English): Background Paragraph: Old age begins in the mid-60s and lasts until the end of life. Most people over 65 have retired from work, freeing up their time for hobbies, grandchildren, and other interests. Stamina, strength, reflex time, and the senses all decline during old age, and the number of brain cells decreases as well. The immune system becomes less efficient, increasing the risk of serious illnesses such as cancer and pneumonia. Diseases such as Alzheimer’s disease that cause loss of mental function also become more common. 
Story: Doctors studied two groups of individuals: group O with people over 65, and group S with people under 65 years old. They published the results in a magazine. 
Question: Which group had fewer people with decreased stamina?
Output (English): group S.