**Core Concept**
The neural tube is formed during embryonic development through the process of neurulation, where the neural folds fuse to close the neural plate. This process is crucial for the formation of the brain and spinal cord.

**Why the Correct Answer is Right**
The direction of fusion of neural folds during the formation of the neural tube is from the midline outward, also known as **cranial-caudal fusion**. This means that the neural folds meet and fuse in the middle, then continue to close towards the cranial and caudal ends. This process is facilitated by the presence of the **notochord**, which provides a midline structure for the neural folds to fuse around.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because fusion of neural folds from the lateral sides inward would result in a failure of neural tube closure, leading to neural tube defects such as spina bifida.

**Option B:** This option is incorrect because fusion of neural folds from the cranial end outward would result in a failure of neural tube closure, leading to cranial neural tube defects.

**Option D:** This option is incorrect because fusion of neural folds from the caudal end outward would result in a failure of neural tube closure, leading to caudal neural tube defects.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that neural tube defects are often associated with genetic mutations, maternal nutritional deficiencies, and environmental factors. The neural tube forms within the first 28 days of gestation, and any defects during this period can lead to severe neurological abnormalities.

**Correct Answer: C. cranial-caudal fusion**