Section B
Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.
Scientists have known since 1952 that DNA is the basic stuff of heredity. They've known its chemical structure since 1953. They know that human DNA acts like a biological computer program some 3 billion bits long that spells out the instructions for making proteins, the basic building blocks of life.
But everything the genetic engineers have accomplished during the past half-century is just a preamble to the work that Collins and Anderson and legions of colleagues are doing now. Collins leads the Human Genome Project, a 15-year effort to draw the first detailed map of every nook and cranny of gene in human DNA. Anderson, who pioneered the first successful human gene-therapy operations, is leading the campaign to put information about DNA to use as quickly as possible in the treatment and prevention of human diseases.
What they and other researchers are plotting is nothing less than a biomedical revolution. Like Silicon Valley pirates reverse-engineering a computer chip to steal a competitor's secrets, genetic engineers are decoding life's molecular secrets and trying to use that knowledge to reverse the natural course of disease. DNA in their hands has become both a blueprint and a drag, a pharmacological substance of extraordinary potency that can treat not just symptoms or the diseases that cause them but also the imperfections in DNA that make people susceptible to a disease.
And that's just the beginning. For all the fevered work being done, however, science is still far away from the Brave New World vision of engineering a perfect human—or even a perfect tomato. Much more research is needed before gene therapy becomes commonplace, and many diseases will take decades to conquer, if they can be conquered at all.
In the short run, the most practical way to use the new technology will be in genetic screening. Doctors will be able to detect all sorts of flaws in DNA long before they can be fixed. In some cases the knowledge may lead to treatments that delay the onset of the disease or soften its effects. Someone with a genetic predisposition to heart disease, for example, could follow a low-fat diet. And if scientists determine that vital protein is missing because the gene that was supposed to make it defective, they might be able to give the patient an artificial version of the protein. But in other instances, almost nothing can be done to stop the ravages brought on by genetic mutations.
What achievements have been got by Collins and Anderson and legions of colleagues？

A. They know that human DNA acts like a biological computer program.
B. They have found the basic building blocks of life.
C. They have accomplished some genetic discovery during the past half-century.
D. They are making a breakthrough in DNA.