Answer:
B. polonium
Explanation:
Polonium (Po) is a very rare and highly volatile radioactive metal. Before Polish-French physicist Marie Curie's discovery of polonium in 1898, uranium and thorium were the only known radioactive elements. Curie named polonium after her homeland, Poland. Polonium was discovered in July 1898 by Marie Skłodowska-Curie and Pierre Curie, when it was extracted from the uranium ore pitchblende and identified solely by its strong radioactivity: it was the first element to be so discovered.
