Respiratory quotient (R.Q.) is

Options

A. Volume of `O_(2)` evolved//Volume of `CO_(2)` consumed
B. Volume of `CO_(2)` evolved//Volume of `O_(2)`
C. Volume of `O_(2)` consumed//Volume of `CO_(2)` evolved
D. Volume of `CO_(2)` consumed//Volume of `O_(2)` evolved

Answer

**Step-by-Step Solution:**

1. **Understanding Respiratory Quotient (R.Q.):**
- The Respiratory Quotient (R.Q.) is a measure used to assess the efficiency of respiration in organisms. It is defined as the ratio of the volume of carbon dioxide produced to the volume of oxygen consumed during respiration.

2. **Identifying the Correct Formula:**
- The formula for R.Q. can be expressed as:
\[ R.Q. = \frac{\text{Volume of CO}_2 \text{ evolved}}{\text{Volume of O}_2 \text{ consumed}} \]

3. **Analyzing the Options:**
- The question provides several options regarding the definition of R.Q.
- Option A: Volume of oxygen evolved into volume of CO2 consumed
- Option B: Volume of carbon dioxide evolved into volume of O2
- Option C: Volume of O2 consumed into volume of CO2 evolved
- Option D: Volume of CO2 consumed into volume of O2 evolved

4. **Selecting the Correct Option:**
- Based on the definition of R.Q., the correct option is:
\[ R.Q. = \frac{\text{Volume of CO}_2 \text{ evolved}}{\text{Volume of O}_2 \text{ consumed}} \]
- This corresponds to Option B: Volume of carbon dioxide evolved into volume of O2.

5. **Conclusion:**
- Therefore, the correct answer to the question "Respiratory quotient (R.Q.) is" is:
\[ \text{Volume of carbon dioxide evolved into volume of oxygen consumed.} \]

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