The correct answer is option 3, Florence Nightingale. She is known as the "Lady with the Lamp" because during the Crimean War, she would make her rounds at night with a lamp in order to check on the wounded soldiers. Florence Nightingale was a pioneering nurse who significantly improved the standard of care for patients in hospitals. She was known for her compassion, dedication, and tireless efforts to improve sanitation and healthcare practices. It is important to note that options 1 and 2, Joan of Arc and Helen Keller, were well-known historical figures, but they are not specifically associated with being the "Lady with the Lamp." Option 4, Sarojini Naidu, was an Indian freedom fighter and poet, but she is not referred to as the "Lady with the Lamp."