Consider the following facts:

1. Radioactivity was discovered by Marie Curie.
2. Radioactive materials produce penetrative rays which have been termed alpha, beta and gamma.
3. While alpha and beta rays are harmful in large amounts, gamma rays pose no danger to human, plant or animal health.

Which of the above is/are true?

In 1896, Henri Becquerel was investigating phosphorescence in uranium salts when he discovered a new phenomenon which came to be called radioactivity. He, Pierre Curie and Marie Curie began investigating the phenomenon. In the process, they isolated the element radium, which is highly radioactive. They discovered that radioactive materials produce intense, penetrating rays of three distinct sorts, which they labeled alpha, beta and gamma after the Greek letters. Some of these kinds of radiations could pass through ordinary matter, and all of them could be harmful in large amounts.