Assertion `:` Lymph is the filtered blood from capillaries, which is rich in oxygen, but devoid of RBC.
Reason `:` RBC can filter out due to small diamerters of fenestra of capillary , but `O_(2)` can not do so.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion .
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are false.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that lymph is filtered blood from capillaries, which is rich in oxygen but devoid of red blood cells (RBCs).
- This is true because lymph is indeed derived from the interstitial fluid that surrounds cells and contains nutrients, oxygen, and waste products, but it does not contain RBCs.

2. **Analyzing the Reason**:
- The reason provided states that RBCs can filter out due to the small diameters of the fenestra (pores) of capillaries, but oxygen cannot do so.
- This statement is misleading. While it is true that RBCs do not pass through the capillary walls due to their size, the reason given does not accurately explain the process of lymph formation. Instead, RBCs remain in the bloodstream, and oxygen is transported by hemoglobin within RBCs.

3. **Conclusion**:
- Since the assertion is true and the reason is false, we conclude that the correct relationship is that the assertion is correct, but the reason is incorrect.

4. **Final Answer**:
- The correct option is option 3: "Assertion is true, but the reason is false."