The answer is D. Einstein.
Henri Becquerel, Roentgen, and Madam Curie were all physicists who made significant contributions to the field of radioactivity. Becquerel discovered radioactivity in 1896, while Roentgen discovered X-rays in 1895. Madam Curie was the first person to win two Nobel Prizes, one in physics and one in chemistry. She is best known for her work on radioactivity, which she discovered with her husband, Pierre Curie.
Einstein, on the other hand, was a theoretical physicist who made significant contributions to the fields of relativity and quantum mechanics. He is best known for his theory of relativity, which revolutionized our understanding of space, time, and gravity. He also developed the theory of quantum mechanics, which revolutionized our understanding of the behavior of matter and energy at the atomic and subatomic level.
While Einstein’s work was groundbreaking, it was not in the field of radioactivity. Therefore, he is the odd one out in this list.