Statement:\nThe hepatitis-B virus, which causes extensive liver damage, may be transmitted through articles of personal use such as toothbrushes, towels, or even handkerchiefs.\nConclusions:\nI. Hepatitis-B is a contagious disease.\nII. The human liver is among the organs most prone to damage by hepatitis-B virus.

Introduction / Context:
We test necessary inference from a health-related statement. The statement notes two things: hepatitis-B causes extensive liver damage, and it may spread via shared personal items (toothbrush, towel, handkerchief). We must identify which conclusions must follow strictly from this text.

Given Data / Assumptions:

• Transmission can occur through shared personal articles.
• The disease damages the liver extensively.
• No inter-organ comparison is offered.

Concept / Approach:
Contagious diseases are those transmissible from person to person by various routes (direct contact, fluids, fomites, etc.). If hepatitis-B can be transmitted through shared personal items, then person-to-person spread via fomites is implied; therefore, it is contagious. However, saying the liver is “among the most prone” organs requires a comparative claim (liver versus other organs), which the statement does not provide. It only asserts that the virus causes extensive liver damage; it does not rank organ susceptibility or say anything about other organs.

Step-by-Step Solution:
1) Conclusion I: Transmission via personal articles → human-to-human spread → contagious → follows.2) Conclusion II: Needs organ-susceptibility comparison; the statement lacks any cross-organ data → does not follow.

Verification / Alternative check:
If the statement had claimed “the liver is the most affected organ compared to others,” II would follow. It does not; it only describes severity for the liver.

Why Other Options Are Wrong:
Only II: unsupported. Either I or II: allows II to be true by necessity, which it is not. Neither: incorrect because I necessarily follows.

Common Pitfalls:
Reading professional knowledge about hepatitis-B beyond the given text; we must stick to exactly what is stated and what it necessitates.

Final Answer:
if only conclusion I follows