Cause & Effect — Public health actions vs biomedical advances.\nI. The municipal corporation has ordered intensive insecticide fogging in all city wards.\nII. Dengue can now be prevented by a vaccine developed by the Immunology Institute of India.

Introduction / Context:
Two different disease-control approaches appear: vector control (fogging) and vaccination. We must decide whether one directly causes the other or whether they are independent lines of action.

Given Data / Assumptions:

• I: Citywide fogging order to reduce mosquito populations.
• II: A dengue-preventive vaccine is available.
• No statement links the vaccine's availability to the fogging order.

Concept / Approach:
Fogging is typically a response to local transmission risk (vector abundance or outbreak). The existence of a vaccine does not directly cause a city to fog; if anything, vaccine availability might reduce reliance on fogging over time, not trigger it.

Step-by-Step Solution:

Verification / Alternative check:
Imagine outbreak conditions: fogging would be ordered regardless of whether a vaccine exists; thus I is not an effect of II.

Why Other Options Are Wrong:
A/B invent cross-causation; D inverts without basis; “None” is less precise than C.

Common Pitfalls:
Assuming all health measures are causally linked rather than parallel responses to risk.

Final Answer:
If I is the effect but II is not its direct/immediate cause.