The respiratory quotient (R. Q.) is less than one in:

Options

A. fats
B. carbohydrates
C. proteins
D. organic acids

Explanation

### Step-by-Step Solution

1. **Understanding Respiratory Quotient (R.Q.)**:
- The respiratory quotient is defined as the ratio of carbon dioxide (CO2) produced to oxygen (O2) consumed during respiration.
- Mathematically, it is expressed as:
\[ R.Q. = \frac{\text{CO2 produced}}{\text{O2 consumed}} \]

2. **Identifying the Values of R.Q.**:
- The value of R.Q. can vary depending on the type of respiratory substrate being used by the organism.
- The common values are:
- R.Q. = 1 for carbohydrates
- R.Q. < 1 for fats and proteins
- R.Q. > 1 for organic acids

3. **Analyzing the Options**:
- **Carbohydrates**: R.Q. = 1
- **Fats**: R.Q. < 1
- **Proteins**: R.Q. < 1
- **Organic Acids**: R.Q. > 1

4. **Conclusion**:
- Since the question asks for the respiratory substrates where the R.Q. is less than 1, the correct answers are fats and proteins.

### Final Answer:
The respiratory quotient (R.Q.) is less than one in **fats and proteins**.

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