The Manhattan Project refers to

a. Allied plans to rescue the inmates of German concentration camps.

b. the project to decipher Japan's diplomatic code.

c. the plan of the United States government to defend New York in the event of enemy attack.

d. the secret plan to build an atomic bomb.

The correct answer is: D: The Manhattan Project refers to the secret plan to build an atomic bomb. It was the project that produced the first nuclear weapon during the World War II, and it was led by the United States of America with the support by Canada and United Kingdom. The first bomb was designed in Los Alamos National Labaratory. The project was active between 1942 and 1946. It resulted in two types of atomic bombs being developed: simple gun-type fission weapon with uranium and a more complex plutonium implosion-type weapon.