The correct answer is D. Population growth.
Population growth is the most responsible for the world water crisis because it leads to increased demand for water. As the population grows, so does the need for water for drinking, bathing, cooking, agriculture, and industry. This increased demand can put a strain on water resources, leading to shortages and even conflict.
Dams can also contribute to the water crisis, as they can block the flow of rivers and reduce the amount of water available for downstream users. Floods can also damage water infrastructure and make it difficult to access clean water. However, these factors are not as significant as population growth in terms of their impact on the water crisis.
In conclusion, population growth is the most responsible for the world water crisis because it leads to increased demand for water. This increased demand can put a strain on water resources, leading to shortages and even conflict.