单选题 Many people imagine that Alzheimer"s disease, the degenerative disorder that ultimately leaves sufferers with total memory loss, is an inevitable result of aging. This is not so. 【C1】______the risks of contracting the disease increase with age, there are many elderly people【C2】______memories are perfect. Most of us are so ill-【C3】______about all forms of memory loss that we label everything "Alzheimer"s". Alzheimer"s disease itself can【C4】______people as young as 30 and can progress either quickly or slowly. It can also【C5】______the blame for other non-degenerative conditions such as deep depression. 【C6】______, only an examination of the brain tissue during all autopsy can produce an accurate【C7】______of the disease. The causes of Alzheimer"s are unknown. They may be either【C8】______or environmental. A study in 1996 of 13, 000 people whose parents or siblings had the disease showed they had five times【C9】______chance of succumbing【C10】______the age of 80 than those with no family【C11】______of the problem. There are other factors, however. In a study of identical twins, it was found that only about half of the twin pairs developed Alzheimer"s and, when both twins【C12】______it, they did so as【C13】______as 15 years apart. The possibility【C14】______environment plays a part was【C15】______by another 1996 study, this time of two groups of elderly Japanese men. One group lived in Hawaii, the other in Japan. The Hawaiian group had a much higher【C16】______of the disease. Aluminum has been blamed for, the development of Alzheimer"s. This is because a high level of aluminum has been found in the brains of sufferers. The disease was first diagnosed at the beginning of the 20th century. It was at this time【C17】______aluminum was becoming widely available for use in cooking pots. Memory loss, difficulty in【C18】______familiar tasks, and problems with abstract thinking are all【C19】______of the onset of the disease. One unusual feature is its impact on language. It attacks nouns first, 【C20】______verbs. Grammar is one of the last things to go.

【正确答案】 C

【答案解析】解析：句意：既有可能是遗传的，也有可能是受生存环境影响的。根据句中的“either…or．．．”结构，可知空白处所填的词应该与“environmental”相对应，根据常识我们知道“环境”是外在因素，而相对应的应该是内在因素genetic“基因，遗传”，C选项符合文意。instinctual“本能的”；natural“自然的”；intuilive“直觉的”。

【正确答案】 D

【答案解析】解析：句意：……调查显示，父母和兄弟姐妹中有患老年痴呆症的人在80岁前患该病的可能性比没有该家庭病史的人的可能性要高出5倍。根据句意和常识可知，家庭中有该病病史的人的患病率肯定要高于没有该病病史的人，只能选择more。slighter“更轻微的”；fainter“更微弱的”；less“更少的”。