阅读理解   On June 26, 2000, two scientific teams announce at the White House that they had deciphered virtually the entire human genome, a prodigious feat that involved determining the exact sequence of chemical units in human genetic material. An enthusiastic President Clinton predicted a revolution in 'the diagnosis, prevention and treatment of most, if not all, human diseases'.
    Now, 10 years later, a sobering realization has set in. Decoding the genome has led to stunning advances in scientific knowledge and DNA-processing technologies but it has done relatively little to improve medical treatments or human health.
    To be fair, many scientists at the time were warning that it would be a long, slow slog to reap clinical benefits.
    And there have been some important advances, such as powerful new drugs for a few cancers and genetic tests that can predict whether people with breast cancer need chemotherapy. But the original hope that close study of the genome would identify mutations or variants that cause diseases like cancer, Alzheimer's and heart ailments—and generate treatments for them—has given way to realization that the causes of most diseases are enormously complex and not easily traced to a simple mutation or two.
    In the long run, it seems likely that the genomic revolution will pay off. But no one can be sure. Even if the genetic roots of some major diseases are identified, there is no guarantee that treatments can be found. The task facing science and industry in the coming decades is at least as challenging as the original deciphering of the human genome.

单选题     Back in the year 2000, what was exciting about the deciphered genome?

单选题     Clinically, according to the passage, the prophecy ten years later ______.

单选题     From our disappointment we have to realize that ______.

单选题     It can be concluded from the passage that ______.

单选题     The writer's tone in the passage is ______.