RQ is

Options

A. `("vol of "CO_2"released in respiration")/("vol of "O_2"consumed in respiration")`
B. `("vol of "CO_2"consumedinphotosynthesis")/("vol of "O_2"consumedin respiration")`
C. `("vol of "CO_2"taken in photosynthesis")/("vol of "CO_2"releasedin respiration")`
D. `("vol of "CO_2"taken in photosynthesis")/("vol of "CO_2"released in photosynthesis")`

Answer

### Step-by-Step Solution:

1. **Understanding RQ**: RQ stands for Respiratory Quotient. It is a measure used to understand the metabolic processes in organisms, particularly in relation to respiration.

2. **Definition of RQ**: The Respiratory Quotient is defined as the ratio of the volume of carbon dioxide (CO2) produced during respiration to the volume of oxygen (O2) consumed during the same process.

3. **Mathematical Representation**: The formula for RQ can be expressed as:
\[ RQ = \frac{\text{Volume of CO2 released}}{\text{Volume of O2 consumed}} \]

4. **Significance of RQ**: RQ helps in assessing the type of substrate being metabolized by the organism. Different substrates (carbohydrates, fats, proteins) yield different RQ values.

5. **Analyzing Options**:
- The correct option states that RQ is the volume of CO2 released in respiration divided by the volume of O2 consumed in respiration.
- Other options incorrectly relate to photosynthesis or mix up the terms.

6. **Conclusion**: The correct definition of RQ is the volume of CO2 released in respiration divided by the volume of O2 consumed in respiration.