DISCUSSION: The answer is in the first paragraph. Lines 5-10 are the most important. Line 10 says that radium and polonium were “previously unknown”.
- CORRECT. Line 10 says no one knew about radium and polonium, the other radioactive elements in pitchblende.
- Doubtful. Scientists knew pitchblende had uranium, and they knew uranium was radioactive. They probably thought pitchblende’s radioactivity came from uranium.
- Careful. We know physicists and chemists disagreed about atoms. This prevented Curie from forming a correct theory of radiation. But maybe physicists and chemists didn’t care much about radiation. They may not have tried to develop theories to explain it.
- Lines 44-46 say it wasn’t clear if atoms existed. So presumably there was some research being done to settle the question. In any case, the passage never claims there wasn’t research.
- We don’t know. Physicists are only mentioned in paragraph 3, for their theories on the atom. We don’t know what they thought about radioactive elements. Maybe they thought there were many, but they hadn’t been discovered yet.
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