Which of these is needed to measure the mass of a rock?

Options

A. A balance
B. A barometer
C. A metric ruler
D. A thermometer

Answer

To determine which instrument is needed to measure the mass of a rock, we can analyze the options provided:

1. **Understanding the Question**: We need to identify the correct instrument for measuring mass.

2. **Evaluating the Options**:
- **Weighing Balance**: This instrument is specifically designed to measure mass. It works by comparing the mass of the object with known masses.
- **Barometer**: This device measures air pressure, not mass. Therefore, it is not suitable for our needs.
- **Metric Ruler**: A metric ruler is used for measuring length, not mass. So, it cannot be used to measure the mass of a rock.
- **Thermometer**: This instrument measures temperature, which is unrelated to mass measurement.

3. **Conclusion**: The only appropriate instrument from the options given that can measure the mass of a rock is the **weighing balance**.

Final Answer: **Weighing Balance**

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