**Core Concept**
In the healing of incised wounds, the formation of new collagen fibrils and a thick layer of growing epithelium are key histological features of the proliferative phase, which begins after the initial inflammatory phase and typically occurs around day 4–5 post-injury.

**Why the Correct Answer is Right**
By day 4–5, the wound has progressed beyond the initial inflammatory phase and entered the proliferative phase. During this stage, fibroblasts become active and produce new collagen fibrils, forming the extracellular matrix. Simultaneously, epithelial cells proliferate and form a thick, growing epithelial layer that covers the wound surface. This histological picture is characteristic of early wound maturation and is observed in wounds that are approximately 4–5 days old.

**Why Each Wrong Option is Incorrect**
Option B: About 1 week – At this stage, the wound may show some collagen formation, but the thick epithelium and prominent collagen fibrils are not yet fully developed. The proliferative phase is still ongoing, and the histological features are more mature than at day 4–5.
Option C: 12–24 hrs – This is the early inflammatory phase; wound is still open, epithelium is thin, and collagen is not yet formed.
Option D: 24–48 hrs – Still in the early inflammatory phase; epithelium is minimal, and collagen deposition has not begun.

**Clinical Pearl / High-Yield Fact**
Remember: **"Collagen appears by day 4–5"** – this is a classic histological marker for the start of true wound healing. In clinical exams, if collagen fibrils and thick epithelium are described, the wound is likely at least 4–5 days old.

✓ Correct Answer: A. 4-5days