Answer the following question: Read the following article and select the best answer. Article: Life on earth depends on water, and there is no substitute for it. The current assumption is that our basic needs for water--whether for drinking, agriculture, industry or the raising of fish--will always have to be met. Given this premise , there are two basic routes we can go; more equal access to water or better engineering solutions. Look at the engineering solutions first. A lot of my research concentrates on what happens to wetlands when you build dams in river basins, particularly in Africa. The ecology of such areas is almost entirely driven by the seasonal changes of the river--the pulse of the water. And the fact is that if you build a dam, you generally spoil the downstream ecology. In the past, such problems have been hidden by a lack of information. But in the near future, governments will have no excuses for their ignorance. The engineers' ability to control water flows has created new kinds of unpredictability, too. Dams in Africa have meant fewer fish, less grazing and less floodplain agriculture, none of which were expected. And there average economic life is assumed to be thirty years. Dams don't exist forever, but what will replace them is not clear. The challenge for the future is to find new means of controlling water. Although GM technology will allow us to breed better dry-land crops, there is no market for companies to develop crops suitable for the micro-climates of the Sahel and elsewhere in Africa. Who is going to pay for research on locally appropriate crops in the Third World? Question: What's the main idea of this passage? - The engineering solutions to water resource and their limitation. - The challenge for the future. - The basic means of controlling water. - The challenge for developing crops.
Answer:
The engineering solutions to water resource and their limitation.