Radioactivity was discovered by

Options

A. Henry Becqueral
B. Rutherford
C. J.J. Thomson
D. Madam Curie

Explanation

**Step-by-Step Solution:**

1. **Identify the Scientists Mentioned:**
- The question asks about the discovery of radioactivity, and four scientists are mentioned: Henry Becquerel, Ernest Rutherford, J.J. Thomson, and Marie Curie.

2. **Research Each Scientist's Contribution:**
- **Henry Becquerel:** In 1896, he discovered radioactivity while studying uranium salts. He observed that they emitted rays that could expose photographic plates.
- **Ernest Rutherford:** In 1918, he conducted experiments that led to the understanding of the nucleus and artificial transmutation but did not discover radioactivity itself.
- **J.J. Thomson:** He is known for discovering the electron and developing the atomic model but did not discover radioactivity.
- **Marie Curie:** She conducted extensive research on radioactivity and discovered elements like radium and polonium but was not the first to discover radioactivity.

3. **Determine the Correct Answer:**
- Based on the contributions of each scientist, Henry Becquerel is credited with the discovery of radioactivity.

4. **Conclusion:**
- Therefore, the correct answer to the question "Radioactivity was discovered by" is **Henry Becquerel**.