**Core Concept**
The anterior neuropore is a critical structure in the development of the central nervous system. It is one of the two openings at the anterior (front) end of the neural tube, which eventually gives rise to the brain and spinal cord.

**Why the Correct Answer is Right**
The anterior neuropore typically closes during the fourth week of embryonic development. This is a crucial step in the formation of the neural tube, as it prevents the entry of amniotic fluid and other substances into the developing brain. The closure of the anterior neuropore is a result of the fusion of the neural folds, which are the ridges of tissue that eventually give rise to the brain and spinal cord.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the anterior neuropore closes earlier than the posterior neuropore, which closes around 26-27 days of gestation.
**Option B:** This option is incorrect because the closure of the anterior neuropore is not a result of the formation of the neural crest, which is a separate process that occurs later in development.
**Option C:** This option is incorrect because the anterior neuropore does not close due to the influence of the notochord, which is a structure that provides axial support to the developing embryo.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the closure of the anterior neuropore is a critical step in the development of the central nervous system, and any defects in this process can lead to severe congenital anomalies.

**Correct Answer:** C. 28 days of gestation