In the summer of 1939, a few months before World War II started, Albert Einstein and a group of Hungarian scientists wrote to President Franklin D. Roosevelt. In this letter they warned Roosevelt that the Nazi’s were conducting (6) ______ research and that the consequences would be dire (7) _____ the Nazis were to win the race to build an atom bomb. They recommended that U.S. become involved in uranium research. As a result (8) _____ this letter, the U.S. joined the atomic race and poured billions of dollars into the development of weaponry. The U.S. won the race and became the first country to build an atomic bomb. The bomb was then (9) _____ in Japan, killing hundreds of thousands of civilians. In 1954, a year before his death, Einstein would refer to the moment (10) _____ he signed the letter to President Roosevelt as the greatest mistake of his life.
6. A. atom. ​B. atomically. ​C. atomics​ D. atomic
7. A. since​ B. If. ​C. as​ D. when
8. A. of ​ B. in ​C. from​ D. to
9. A. uses​ B. use ​ C. used​ D. using
10. A. that​ B. whom ​C. where​ D. which