Henri Becquerel discovered natural radioactivity in 1896. He was studying the fluorescence of uranium salts when he noticed that they emitted a type of radiation that could pass through paper and even blackened photographic plates. This radiation was later found to be caused by the decay of uranium atoms.
Marie Curie and her husband Pierre Curie were the first to isolate the elements radium and polonium, which are both radioactive. They also studied the properties of radioactivity and its effects on living things.
Ernest Rutherford was a physicist who studied the nature of radioactivity. He discovered that alpha particles, beta particles, and gamma rays are all types of radiation that are emitted by radioactive elements. He also developed the theory of alpha decay, which explains how radioactive elements decay.
Enrico Fermi was an Italian physicist who made many important contributions to the field of nuclear physics. He was the first to produce a controlled nuclear chain reaction, which is the basis for nuclear power plants. He also developed the theory of beta decay, which explains how radioactive elements decay.
In conclusion, the correct answer to the question “Natural radioactivity was discovered by” is C. Henri Becquerel.