The following passage is an excerpt from a letter from scientist Albert Einstein to US president Franklin Roosevelt. Read the excerpt and then answer question that follows. Some recent work by E. Fermi and L. Szilard, which has been communicated to me in manuscript, leads me to expect that the element uranium may be turned into a new and important source of energy in the immediate future. . . . This new phenomenon would . . . lead to the construction of bombs, and it is conceivable . . . that extremely powerful bombs of a new type could thus be constructed. A single bomb of this type, carried by a boat and exploded in a port, might very well destroy the whole port as well as some of the surrounding territory. However, such bombs might prove to be too heavy for transportation by air. In view of this situation, you may think it desirable to have some permanent contact between the Administration and the group of physicists working on chain reactions in America.

Based on the lesson, which event was a direct result of Einstein’s letter?