"It begins as a single cell and grows into a merciless disease that claims millions of lives year after year. But scientists are steadily unlocking its mysteries and the fight against it, may now have reached a dramatic turning point. New discoveries promise better therapies and hope in the war against ....". The disease referred to in the above quotation is

A. Cancer

B. AIDS

C. Tuberculosis

D. Alzheimer's disease

Answer: Option A