Under the same conditions, two gases have the same number of molecules. They must

Options

A. be noble gases
B. have equal volumes
C. have a volume of `22.4 dm^(3)` each
D. have an equal number of atoms

Answer

To solve the question, we need to refer to Avogadro's hypothesis, which states that equal volumes of gases, at the same temperature and pressure, contain an equal number of molecules.

### Step-by-Step Solution:

1. **Understand the Question**: The question states that under the same conditions, two gases have the same number of molecules. We need to determine what this implies about the gases.

2. **Recall Avogadro's Hypothesis**: According to Avogadro's hypothesis, if two gases have the same number of molecules, they must occupy the same volume when measured at the same temperature and pressure.

3. **Conclusion**: Therefore, if two gases have the same number of molecules under the same conditions, they must have equal volumes.

4. **Select the Correct Option**: Based on the understanding of Avogadro's hypothesis, the correct answer to the question is that the two gases must have equal volumes.

### Final Answer:
Under the same conditions, if two gases have the same number of molecules, they must have equal volumes.

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