The correct option is D Physically weak but mentally indomitable
Paragraph 2 mentions the condition of Florence Nightingale when she arrived in England. It says that she was in a poor state of health and needed rest to recuperate as per the advice of the doctors. But, compassionate as she was, she refused to rest and wanted to continue improving the health of the people. Though she was weak physically, her mental determination and her indomitable spirit kept her alive. So, we can say that the most appropriate way to describe her character, according to paragraph 2, is option D.