The correct answer is B. 235.
Explanation
The anatomic bomb is a device of mass destruction used in warfare that gains its destructive force from nuclear reactions. One of its main characteristics is the formation of a mushroom-shaped cloud when it is detonated. Fissile isotopes, such as uranium-235 or plutonium-239, are necessary for its manufacture. Another important fact about atomic bombs is that they were first developed by the United States during World War II to avenge the attack on Pearl Harbor. Therefore, the correct answer is B. 235.
The complete sentence remains "To create the atomic bomb they needed uranium - 235 the most"
