题目内容：
根据以下材料，回答题More about Alzheimer's Disease
Scientists have developed skin tests that may be used in the future to identify people with Alzheimer's diseasel and may ultimately allow physicians to predict 51_______ is at risk of getting this neurological disorder.
The only current means of 52_______ the disease in a living patient is a long and expensive series of tests that eliminate every other cause of dementia.
"Since Alois Alzheimer described the 53_______ nearly a century .ago, people have been trying to find a way to 54_______ diagnose it in its early stages, " said Patricia Grady, acting director of the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland. "This discovery, if 55_______ , could prove a big step forward in our efforts to deal with and understand the disease. "
Alzheimer's is the single greatest 56_______ of mental deterioration in older people, affecting between 2.5 million and 4 million people in the United States 57_______. The devastating disorder gradually destroys memory and the ability to function, and eventually causes death. There is currently no known 58_______ for the disease.
Researches 59_______ that the skin cells of Alzheimer's patients have defects that interfere with their ability to regulate the flow of potassium in and out of the cells. The fact that the cell defects are present in the skin suggests that Alzheimer's 60_______ from physiological changes throughout the body, and that dementia may be the first noticeable 61_______ of these changes as the defects affect the cells in the brain, scientists said.
The flow of potassium is especially critical in cells responsible for memory formation. The scientists also found two other defects that affect the cells' supply of calcium, another 62_______ element.
One test developed by researches calls 63_______ growing skin cells in a laboratory culture and then testing them with an electrical detector to determine if the microscopic tunnels that 64_______ the flow of potassium are open. Open potassium channels create a unique electrical signature.
A spokesman for the Alzheimer's Association said that if the validity of the diagnostic test can be proven it would be an important 65_______, but cautioned that other promising tests for Aizheimer's have been disappointing.
回答(51)题 A．what
B．one
C．it
D．who
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