**Core Concept:**
Sickle cell disease (SCD) is an inherited genetic disorder caused by a mutation in the HBB gene, which codes for the beta-globin subunit of hemoglobin (Hb). In homozygous form (SS), it results in sickle-shaped red blood cells, leading to anemia, vaso-occlusion, and chronic complications. In heterozygous form (AS), individuals have sickle cell trait (SCT), which is asymptomatic but may cause hemolysis and anemia when combined with other hemoglobinopathies.

**Why the Correct Answer is Right:**
In this scenario, the mother is homozygous for sickle cell disease (SS), while the father is normal (AA). According to the Punnett square probability theory, the possible combinations of Hb genotypes for their offspring are:

1. Homozygous sickle cell disease (SS): This results in sickle cell disease in their children.
2. Homozygous normal (AA): This results in a normal child.
3. Heterozygous sickle cell trait (AS): This results in a child with sickle cell trait.
4. Homozygous sickle cell trait (AS): This results in a child with sickle cell disease (SS) if this genotype is inherited from both parents.

**Why Each Wrong Option is Incorrect:**
A. This option is incorrect because the mother is homozygous for sickle cell disease, which means she cannot pass on the homozygous sickle cell trait (AS) to her child.
B. This option is incorrect because the father is normal (AA), not sickle cell trait (AS), preventing the inheritance of sickle cell trait to the child.
C. This option is incorrect because the mother is homozygous for sickle cell disease (SS), which means she cannot pass on the heterozygous sickle cell trait (AS) to her child.
D. This option is incorrect because the father is normal (AA), not sickle cell trait (AS), preventing the inheritance of sickle cell trait to the child.

**Clinical Pearl:**
When assessing a couple with a history of SCD, it is essential to consider these genotype possibilities for their offspring. Inheritance of sickle cell traits or diseases can have significant clinical implications, including the risk of producing a child with severe SCD. Genetic counselling is crucial in such cases to explain the genotype possibilities and ensure informed reproductive choices.

**Correct Answer Explanation:**
The correct answer is D: Homozygous normal (AA) genotype for both parents (mother and father). This results in a normal child (AA) genotype as well.

In conclusion, the correct answer is D because both parents are homozygous for the normal genotype (AA), meaning they can only pass on the normal genotype (AA) to their child. The inheritance of sickle cell traits or diseases depends on the genotypes of the parents. In the presence of a sickle cell trait (AS) in one parent and homozygous normal (AA) in the other, the child can have either homozygous normal (AA) or heterozygous sickle cell disease (AS).