In absolute dating, age of the rock/fossil is determined by

Options

A. Depth of rock
B. Exposure of rock
C. Decay of radio isotope
D. Rate of surface erosion of rock.

Answer

**Step-by-Step Solution:**

1. **Understanding Absolute Dating:**
- Absolute dating is a method used to determine the exact age of rocks or fossils. It provides a numerical age rather than a relative age.

2. **Identifying the Method Used:**
- The primary method of absolute dating is radioactive dating. This technique measures the decay of radioactive isotopes present in the rocks or fossils.

3. **Radioactive Isotopes:**
- Radioactive isotopes are unstable elements that decay over time into stable elements. Common isotopes used in dating include Uranium-238 and Carbon-14.

4. **Half-Life Concept:**
- Each radioactive isotope has a specific half-life, which is the time it takes for half of the radioactive atoms in a sample to decay. By measuring the remaining amount of the isotope in a sample, scientists can calculate the age of the rock or fossil.

5. **Conclusion:**
- Therefore, in absolute dating, the age of the rock or fossil is determined by the decay of radioactive isotopes and their respective half-lives.

**Final Answer:**
The age of the rock/fossil in absolute dating is determined by the decay of radioactive isotopes.

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