Read the following passage and answer the questions that follow.

Marie Curie was one of the most accomplished scientists in history. Together with her husband, Pierre, she discovered radium, an element widely used for treating cancer. She also studied uranium and other radioactive substances. Pierre and Marie's amicable collaboration later helped unlock the secrets of the atom.

Marie was born is 1867 in Warsaw, Poland, where her father was a professor of Physics. At an early age, she displayed a brilliant mind and a blithe personality. Her great exuberance for learning prompted her to continue with her studies even after high school. She became disgruntled, however, when she learned that the University in Warsaw was closed to women. Determined to receive a higher education, she defiantly left Poland and in 1891 entered the Sorbonne, a French University, where she earned her master's degree and doctorate in Physics. Marie was fortunate to have studied at the Sorbonne with some of the greatest scientists of her day, one of whom was Pierre Curie. Marie and Pierre spent many productive years working together in the Physics laboratory. A short time after they discovered radium, Pierre was killed by a horse-drawn wagon in 1906. Marie was heartbroken. Despondently she recalled their relationship and the joy that they had shared in scientific research.

Marie Curie herself suffered from a fatal illness from her long exposure to radium. However, her feeling of desolation began to fade when she was asked to work as a Physics professor at the Sorbonne. She was the first woman to be given a professorship at the world famous University. In 1911, she received the Nobel Prize in Chemistry.

Pierre died due to