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: Two groups of people participated in a geriatrics study. Group D had people over 65 years old, while group Y had people in their 40's in its composition. 
Question: Which group had people with stronger immune systems?
Output (English): group Y.