[A] : Reduced blood can carry more `CO_2` than oxygenated blood.
[R]: Blood containing more `CO_2` will take up relatively less `C_2 `

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

To solve the question, we need to analyze both statements: the assertion (A) and the reason (R).

### Step 1: Understand the Assertion (A)
The assertion states that "Reduced blood can carry more `CO_2` than oxygenated blood."
- **Explanation**: Reduced blood refers to deoxygenated blood, which is blood that has released its oxygen to the tissues and has picked up carbon dioxide (CO2) from the tissues. This blood is rich in CO2 because it has just returned from the body's tissues where it has collected CO2 as a waste product of metabolism. Therefore, this assertion is **true**.

### Step 2: Understand the Reason (R)
The reason states that "Blood containing more `CO_2` will take up relatively less `O_2`."
- **Explanation**: This statement is also true. According to the principles of gas exchange and the Bohr effect, when blood has a high concentration of CO2, it tends to have a lower affinity for oxygen. This means that as CO2 levels increase, the ability of hemoglobin to bind with oxygen decreases. Therefore, this reason is also **true**.

### Step 3: Determine the Relationship Between A and R
Now we need to assess whether the reason (R) correctly explains the assertion (A).
- While both statements are true, the reason does not directly explain why reduced blood can carry more CO2 than oxygenated blood. The assertion is based on the fact that reduced blood has already released its oxygen and is now carrying CO2, while the reason discusses the relationship between CO2 concentration and oxygen binding.

### Conclusion
- The assertion (A) is true.
- The reason (R) is true, but it does not correctly explain the assertion.
- Therefore, the correct answer is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion.

### Final Answer
- **B**: Both A and R are true, but R is not the correct explanation of A.

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