Throughout July 1945, the Japanese mainland, from Tokyo on Honshu northward to the coast of Hokkaido, were bombed as if an invasion were about to take place. In fact, something far more threatening was at hand, as the Americans were telling Stalin at Potsdam.（伯茨坦）
In 1939 physicists in the United States had learned of experiments in Germany showing the possibility of atomic power and understood the coming damage of an atomic bomb. On August 2, 1939, Albert Einstein warned President Roosevelt of the danger of Nazi Germany’s advances in development of the atomic bomb. Eventually, the U.S. Office of Scientific Research Development was created in June 1941 and given combined responsibility with the War Department in the Manhattan Project to develop a nuclear bomb. After four years of research and development efforts, an atomic device was set off on July 16, 1945, in a desert area at Alamogordo, New Mexico, producing an explosive power equal to that of more than 15,000 tons of TNT. Thus, the atomic bomb was born. Truman, the new U.S. president, believed that this terrible object might be used to defeat Japan in a way less costly of U.S. lives than an ordinary invasion of the Japanese homeland. Japan’s unsatisfactory reply to the Allies’ Potsdam Declaration decided the matter.
On August 6, 1945, an atomic bomb, carried from Tinian Island in the Mariana in a specially equipped B-29 was dropped on Hiroshima, at the southern end of Honshu. The combined heat and explosion destroyed everything in the explosion’s immediate neighbourhood , produced fires that burned out almost 4.4 square miles completely, and killed between 70,000 and 80,000 people, in addition to injuring more than 70,000 others. A second bomb dropped on Nagasaki on August 9, killed between 35,000 and 40,000 people, injured a like number and ruined 1.8 square miles.
What is the main idea of the passage?

A．An atomic bomb was dropped on Hiroshima and Nagasaki.

B．After research and development efforts, an atomic bomb was born.

C．An invasion was about to take place with the use of the atomic bomb.

D．The birth and use of the atomic bomb ended the Second World War.

Albert Einstein warned Roosevelt of _________.

A．Nazi Germany’ success in making an atomic bomb

B．the possibility of atomic power from Nazi Germany

C．Japan’s unsatisfactory reply to the Allies’ Potsdam Declaration

D．destruction of everything from the explosion of the atomic bomb

What made the U.S. decide to drop the atomic bombs over Japan?

A．Truman’s becoming the president of the United States.

B．The great destruction power of the atomic bomb.

C．Reducing the cost of its lives.

D．Not being content with Japan’s reply.

How many people were killed by the two bombs dropped in Japan?

A．Between 105,000 and 120,000 people.

B．Between 35,000 and 40,000 people.

C．Between 70,000 and 80,000 people.

D．Between 140,000 and 150,000 people.