Concept:Transport modes that depend on natural water bodies are highly sensitive to changes in water availability and flow.
Explanation:River transport needs enough water depth for boats to move safely.
During drought, rivers may dry up or become too shallow for vessels.
During floods, strong currents and hidden obstacles make river navigation risky.
Ocean transport mostly uses open seas, while road and air transport do not depend on river water levels.
Hence, both drought and flood directly disrupt river transport more than the other options.
Answer:D. river transport