**Core Concept**
In forensic virology, tissue samples must be preserved to maintain viral integrity for accurate detection and study. The ideal storage medium must prevent degradation of viral particles while allowing long-term stability without denaturing the virus.

**Why the Correct Answer is Right**
50% glycerine is a preferred fixative for storing tissue samples during virological autopsies. It preserves viral antigens and RNA/DNA structures effectively by maintaining the tissue’s morphology and preventing enzymatic degradation. Glycerine’s high viscosity and non-reactive nature prevent viral RNA from being broken down, making it ideal for future virological analysis. This concentration balances preservation with tissue flexibility.

**Why Each Wrong Option is Incorrect**
Option A: Sodium chloride is a saline solution that provides osmotic balance but does not preserve viral components; it lacks antiviral or fixative properties and leads to rapid degradation of viral material.
Option B: Alcohol (e.g., 70–95%) rapidly denatures proteins and RNA, destroying viral nucleic acids and rendering them undetectable in virological studies.
Option C: Rectified spirit (95% ethanol) is highly denaturing and causes irreversible damage to viral genetic material, making it unsuitable for virology.

**Clinical Pearl / High-Yield Fact**
Always use 50% glycerine for storing tissue in virological autopsies — it preserves viral RNA and antigens better than any alcohol-based solution. Never use alcohol or saline for virology preservation.

✓ Correct Answer: D. 50% glycerine