Multiple choice

Which one of the following is radioactive?

  1. Cesium

  2. Platinum

  3. Strontium

  4. Thorium
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Thorium is a naturally radioactive element (atomic number 90) found in monazite sands. All thorium isotopes are radioactive, with Th-232 being the most abundant. While cesium, strontium, and platinum can have radioactive isotopes, they are not inherently radioactive in their natural form. Strontium-90 and Cesium-137 are fission products, not naturally occurring.

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