## Core Concept
The "banana sign" and "lemon sign" are two ultrasound markers used in fetal imaging to detect potential neurological and skeletal anomalies. The **banana sign** refers to the abnormal curvature of the fetal cerebellum, which resembles a banana, often associated with neural tube defects (NTDs) such as spina bifida. The **lemon sign** refers to the scalloping of the frontal bones of the fetal skull, giving it a lemon-like appearance, also associated with NTDs.

## Why the Correct Answer is Right
The correct answer, **Spina Bifida**, is associated with both the banana and lemon signs. In spina bifida, particularly the open type, there is a defect in the closure of the neural tube during fetal development. This can lead to the herniation of neural tissue and meninges through a defect in the vertebral column. The **banana sign** is seen due to the downward displacement of the cerebellum through the foramen magnum, altering its normal curvature. The **lemon sign** is observed due to the deformation of the frontal bones of the skull, possibly related to the altered intracranial pressure dynamics or the mechanical forces exerted by the herniated neural tissue.

## Why Each Wrong Option is Incorrect
- **Option A: Congenital Heart Disease** - While congenital heart diseases are significant fetal anomalies, they are not directly associated with the banana and lemon signs. These signs are more specific to neural tube defects.
- **Option B: Down Syndrome** - Down syndrome is a chromosomal abnormality that can present with various ultrasound markers, but the banana and lemon signs are not typically associated with this condition. Markers for Down syndrome include nuchal translucency, nasal bone, and others.
- **Option C: Fetal Growth Restriction** - Fetal growth restriction (FGR) refers to a condition where a fetus does not grow at a normal rate inside the womb. While serious, FGR is not directly linked to the banana and lemon signs.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that the presence of the **banana sign** is highly suggestive of a neural tube defect, particularly spina bifida. The **lemon sign**, while not as specific, can also indicate potential NTDs or other conditions affecting fetal development. These signs are critical for prenatal diagnosis and may prompt further investigation, such as amniocentesis for alpha-fetoprotein levels.

## Correct Answer Line
**Correct Answer: C. Spina Bifida**