Assertion: The person heterozygous for sickle-cell trait produces both normal `(Hb^A)` and abnormal haemoglobin `(Hb^S)`.
Reason: The normal allele and the sickle-allele are codominant.

Options

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

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that a person who is heterozygous for sickle-cell trait produces both normal hemoglobin (Hb^A) and abnormal hemoglobin (Hb^S).
- A heterozygous individual has two different alleles for a gene, in this case, one normal allele (Hb^A) and one sickle allele (Hb^S).

2. **Understanding the Reason**:
- The reason provided states that the normal allele (Hb^A) and the sickle allele (Hb^S) are codominant.
- Codominance means that both alleles in a heterozygous individual contribute to the phenotype, and both are expressed equally.

3. **Linking Assertion and Reason**:
- Since the assertion claims that a heterozygous individual produces both types of hemoglobin, and the reason explains that this occurs because the alleles are codominant, we can see that the reason supports the assertion.

4. **Determining the Truth of Assertion and Reason**:
- Both the assertion and the reason are true. The heterozygous individual does produce both types of hemoglobin, and the reason correctly explains this phenomenon through the concept of codominance.

5. **Conclusion**:
- Therefore, both the assertion and reason are true, and the reason is the correct explanation of the assertion.

### Final Answer:
Both the assertion and reason are true, and the reason is the correct explanation of the assertion.