Enamel, being the hardest body tissue, is composed of:

Enamel is indeed the hardest substance in the human body, and its composition is crucial for its strength and function. The correct answer states that enamel is composed of 95.5% inorganic material, which primarily consists of hydroxyapatite crystals, providing the hardness and resilience needed to withstand the forces of chewing and biting. The presence of 0.5% organic material, mainly proteins and lipids, plays a minor role in the structure and formation of the enamel but is not a significant portion. Additionally, the 4% water content is essential for maintaining the enamel's integrity and facilitating some degree of permeability, but it is also a minimal portion compared to the inorganic content.

The high inorganic content is what gives enamel its exceptional hardness and makes it the most durable part of the tooth. Understanding this specific composition helps in recognizing why enamel can resist decay and mechanical wear, as well as its role in overall dental health. The values given in the other choices do not accurately reflect the typical composition of enamel, particularly the proportions of organic and inorganic materials, which are essential for proper characterization.