**Core Concept**
Achondroplasia is a genetic disorder that results in dwarfism, caused by a mutation in the **FGFR3 gene**. This condition is usually inherited in an **autosomal dominant** manner.

**Why the Correct Answer is Right**
When both parents have achondroplasia, they can be either homozygous or heterozygous for the mutated **FGFR3 gene**. If both are heterozygous, there's a 25% chance of having a homozygous child (more severely affected), a 50% chance of having a heterozygous child (similarly affected as the parents), and a 25% chance of having a homozygous normal child.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it overestimates the chance of having a normal child.
**Option B:** This option is incorrect because it underestimates the chance of having a normal child.
**Option D:** This option is incorrect because it suggests no chance of having a normal child, which is not true for heterozygous parents.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **autosomal dominant** conditions have a 50% chance of being passed to each offspring, but the severity can vary, especially in cases like achondroplasia where homozygosity can lead to a more severe phenotype.

**Correct Answer:** C. 25%.