One of the most pressing challenges that the United States--and indeed, the world--will fa

ce in the next few decades is how to alleviate the growing stress that human activities are placing on the environment. The consequences are just too great to ignore. Wildlife habitats are being degraded or disappearing altogether as new developments take up more land. Plant and animal species are becoming extinct at a greater rate now than at any time in Earth's history. As many as 30 percent of the world's fish stocks are overexploited. And the list goes on.

Yet, there is reason to have hope for the future. Advances in computing power and molecular biology are among the tremendous increases in scientific capability that are helping researchers gain a better understanding of these problems. Recent developments in science and technology could provide the basis for some major, and timely actions that would improve our understanding of how human activities affect the environment.

One priority for research is improving hydrological forecasting. It has been estimated that the world's water use could triple in the next two decades. Already, widespread water shortages have occurred in parts of China, India, North Africa, and the Arabian Peninsula. The need for water also is taking its toll on freshwater ecosystems in the United States. Only 2 percent of the nation's streams are considered in good condition, and close to 40 percent of native fish species are rare to extinct. Using a variety of new remote sensing tools, scientists can learn more about how precipitation affects water levels, how surface water is generated and transported, and how changes in the landscape affect water supplies.

To prevent outbreaks of infectious diseases in plants, animals, and humans, more study is needed on how pathogens, parasites, and disease-carrying species--as well as humans and other species they infect--are affected by changes in the environment. The overuse of antibiotics both in humans and in farm animals has contributed to the growth of antibiotic-resistant microorganisms. Researchers can take advantage of new technologies in genetics and computing to better monitor and predict the effects that environmental changes might have on disease outbreaks.

Humans have made alterations to Earth's surface--such as tropical deforestation, reduction of surface and ground water, and massive development--so dramatic that they approach the levels of transformation that occurred during glacial periods. Such alterations cause changes in local and regional climate, and will determine the future of agriculture. Recent advances in data collection and analysis should be used to document and better understand the causes and consequences of changes in land cover and use.

The sentence "And the list goes on." (Para. 1) is used to suggest that

A．there are many more ways in which humans are hurting the environment.

B．environmental degradation is continuing unabated.

C．the total of animal and plant species facing extinction are too numerous to list.

D．in addition to fish, many other plant and animal species face over-exploitation by humans.