**Core Concept**
The "Lemon sign" and "Banana sign" are ultrasound markers associated with spina bifida, a congenital neural tube defect. These signs are observed during antenatal ultrasound examination.

**Why the Correct Answer is Right**
The "Lemon sign" is characterized by a flattening of the frontal bone, resembling a lemon, due to the herniation of the cerebellum through the foramen magnum. This occurs because the normal curvature of the frontal bone is disrupted by the upward displacement of the cerebellum. The "Banana sign" is seen as a curvature of the cerebrum, resembling a banana, due to the herniation of the cerebellum through the foramen magnum. This curvature occurs because the normal shape of the cerebrum is altered by the downward displacement of the cerebellum.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not relate to spina bifida or the specific ultrasound markers of the "Lemon sign" and "Banana sign".
**Option B:** This option is incorrect because it is a different congenital condition altogether, and not related to the specific ultrasound markers in question.

**Clinical Pearl / High-Yield Fact**
The "Lemon sign" and "Banana sign" are significant markers for spina bifida, and their presence warrants further evaluation and monitoring of the fetus. These signs are often associated with other congenital anomalies and require a multidisciplinary approach to management.

**Correct Answer: C. Spina Bifida**