**Core Concept**
A bulging anterior fontanelle is a clinical sign indicating increased intracranial pressure (ICP) in infants. This occurs when the pressure inside the skull exceeds the pressure of the surrounding cranial bones, leading to the soft bones of the anterior fontanelle bulging outward.

**Why the Correct Answer is Right**
The bulging anterior fontanelle is a manifestation of raised ICP, which can be caused by various conditions such as hydrocephalus, meningitis, or subdural hematoma. The anterior fontanelle is the soft, unossified area at the front of the infant's skull, and its bulging is a visible sign of the body's attempt to compensate for the increased pressure within the cranial vault. The fontanelle's bulging is often accompanied by other signs of raised ICP, such as a tense and bulging posterior fontanelle, scalp tenderness, and a high-pitched cry.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a normal fontanelle in an infant does not bulge; rather, it may be slightly depressed or flat.
**Option B:** This option is incorrect because a bulging posterior fontanelle is a sign of raised ICP in infants, but it is not the same as a bulging anterior fontanelle.
**Option D:** This option is incorrect because a fontanelle that closes prematurely may be a sign of cranial dysplasia or other bone disorders, but it is not directly related to raised ICP.

**Clinical Pearl / High-Yield Fact**
Remember the "3 Ps" of increased ICP in infants: **P**osture (infants with raised ICP often sit or lie with their head in a position that reduces ICP), **P**osterior fontanelle (tense and bulging), and **P**osition (infants with raised ICP often have a high-pitched cry).

**Correct Answer: C. Hydrocephalus**