Cause & Effect — Natural disaster chain.\nI. Thousands of people drowned and hundreds of houses were swept away in Japan.\nII. A very high-intensity earthquake occurred off the Japanese coastline.

Introduction / Context:
Major offshore earthquakes can trigger tsunamis and severe coastal inundation, producing drownings and destruction. The question asks for the immediate causal direction between the disaster outcomes (I) and the seismic event (II).

Given Data / Assumptions:

• II: A high-intensity earthquake off the coast.
• I: Mass drownings and sweeping away of houses in Japan.
• Earthquakes at sea frequently cause tsunamis; tsunamis cause coastal devastation.

Concept / Approach:
Seismic event → tsunami/inundation → drownings & structural loss. Hence II is the immediate cause; I is the effect.

Step-by-Step Solution:

Verification / Alternative check:
Even if landslides or aftershocks contribute, they stem from the primary seismic event.

Why Other Options Are Wrong:
A reverses direction; C/D claim non-causality; “None” is unnecessary.

Common Pitfalls:
Missing the tsunami step; still, II remains the proximate trigger.

Final Answer:
If II is the immediate cause and I is its effect.