Senility refers to great losses of intellectual capacity that occurs in old age and is associated with the widespread loss of nerve cells and the shrinkage of brain tissue. Senility is a great decline from a previous intellectual【B1】in an aging person. Memory is the mental capacity most often affected. The memory loss may first show itself clearly in simple absentmindedness or a tendency to forget or【B2】things and repeat oneself in conversation. As the senility progresses, the loss of memory【B3】in scope until the patient can no longer remember basic social and【B4】skills or function independently. There may also be declines in the person"s language skills, spatial or temporal orientation,【B5】or other cognitive capacities and personality changes may also be【B6】to see. Senility usually has a slow, gradual onset and is most common in persons over age 75. The most common cause of the syndrome is Alzheimer"s disease, which【B7】for about 50 percent of all elderly persons with unbalanced mind and is hard to restore a former state. The second most common cause is vascular senility which arises from hypertension (high blood pressure) or some other vascular condition. In this type, a series of small strokes progressively destroy small【B8】of the brain, eventually leading to senility. There is no【B9】for Alzheimer"s disease, but vascular senility can sometimes be prevented or its【B10】slowed by treatment of the underlying systemic vascular disorder. Among other significant causes of senility in the elderly are Huntington"s chorea, Parkinson"s disease, and multiple sclerosis. 【B1】

A. level
B. extent
C. scope
D. criterion