Step 1: Understanding the Concept
The respiratory quotient (RQ) compares the carbon dioxide given out with the oxygen taken in during respiration.
Step 2: Formula
\(\text{RQ}=\dfrac{\text{volume of CO}_{2}\text{ released}}{\text{volume of O}_{2}\text{ consumed}}\)
It is 1 for carbohydrates, less than 1 for fats and proteins, and infinite in anaerobic respiration.
Step 3: Compare the options
Options (A) and (B) use wrong terms such as carbon dioxide consumed or oxygen evolved, and (C) is the inverted ratio.
Only (D) is correct.
Final Answer:
RQ is carbon dioxide released divided by oxygen consumed, option (D).
\[ \boxed{\text{(D) }\dfrac{\text{CO}_{2}\text{ released}}{\text{O}_{2}\text{ consumed}}} \]