Question: Q: When the hydrogen is nearly used up, the star can fuse which element into heavier elements? Choices: - carbon - xenon - oxygen - helium A:
Answer: helium

Question: Q: What is the term for the breakdown of unstable isotopes into stable elements? Choices: - isotopic decay - radioactive decrease - secondary decay - radioactive decay A:
Answer: radioactive decay

Question: Q: Enzymes - proteins which speed up what? Choices: - crystals reactions - liquid reactions - physical reactions - chemical reactions A:
Answer:
chemical reactions