Assertion : In Balanoglossus, proboscis is involved in excretion
Reason : Glomerulus is present in proboscis.

Options

A. If both assertion & reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both assertion & Reason are true but the reason is not the correct explanation of the assertion, them mark (2).
C. If assertion is true statement but reason is false, them mark (3).
D. If both assertion and reason are false statements, them mark (4).

Explanation

### Step-by-Step Solution:

1. **Understanding the Organism**:
- Balanoglossus is a member of the phylum Hemichordata. It has a body divided into three main parts: the proboscis, collar, and trunk.

2. **Analyzing the Assertion**:
- The assertion states that in Balanoglossus, the proboscis is involved in excretion.
- The proboscis is indeed the anterior part of the body and plays a role in the removal of nitrogenous waste, confirming that the assertion is true.

3. **Analyzing the Reason**:
- The reason states that a glomerulus is present in the proboscis.
- A glomerulus is a tuft or cluster of capillaries that is typically involved in the filtration of blood in the kidneys of vertebrates. In Balanoglossus, the glomerulus is found in the proboscis gland, which supports the function of excretion.

4. **Conclusion**:
- Both the assertion and the reason are true. Furthermore, the reason provides a correct explanation for the assertion, as the presence of the glomerulus in the proboscis is directly related to its role in excretion.

5. **Final Answer**:
- Therefore, the correct option is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.