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问题 选择题

下列图形：正三角形、平行四边形、矩形、菱形、正方形、等腰梯形、直角梯形、圆，其中既是中心对称图形，又是轴对称图形的共有（　　）

A．3个

B．4个

C．5个

D．6个

答案

①是轴对称图形，不是中心对称图形；

②是中心对称图形，不是轴对称图形；

③矩形既是中心对称图形，又是轴对称图形；

④菱形既是中心对称图形，又是轴对称图形；

⑤正方形既是中心对称图形，又是轴对称图形．

⑥是轴对称图形，不是中心对称图形；

⑦既不是轴对称也不是中心对称；

⑧既是轴对称也是中心对称；

故③④⑤⑧符合题意．

故选B．

问答题

A 17-year U. S. study has finally answered one of the most pressing questions about diabetes: Can tight control of blood sugar prevent heart attacks and strokesThe answer, reported Thursday in The New England Journal of Medicine, is yes. Intense control can reduce the risk by nearly half. And, the study found, the effect occurred even though the patients had only had a relatively brief period of intense blood sugar control when they were young adults. None the less, more than a decade later, when they reached middle age, when heart disease and strokes normally start to appear, they were protected. The study involved those with Type 1 diabetes, which usually arises early in life and involves the death of insulin-secreting cells. The question of whether rigid blood sugar control protects against heart disease and strokes has divided the field for decades, diabetes researchers said. "It’s really a major question that has been around for a long time," said Dr. Judith Fradkin, who directs diabetes research at the National Institute of Diabetes and Digestive and Kidney Diseases, Researchers knew that diabetes was linked to heart disease — at least two-thirds of diabetics die of heart disease. But although studies showed that controlling blood sugar protects against damage to the eyes, kidneys and nerves, there was no conclusive evidence that it would have the same effect on heart disease and strokes. "In that sense, this is a landmark study," said Fradkin. But the result also gives rise to questions: Does the same effect occur in people with Type 2 diabetes, which usually occurs later in life and involves an inability to respond to insulin And why would tight control of blood sugar for one brief period have such a pronounced effect laterFradkin said she expected the results would hold for Type 2 diabetes. Another large U. S. federal study is addressing that question, she notes, but it is already known that tight control of blood sugar in Type 2 diabetes protects against nerve, kidney and eye damage, just as it does with Type 1 diabetes. In addition, a study in Britain hinted — although it did not demonstrate — that Type 2 diabetics who keep their blood sugar low have less heart disease and strokes. Fradkin said she hoped the emerging evidence and improving therapies would make a difference.
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多项选择题

C肽测定的主要用途有（）

A.评估胰岛素分泌

B.评估空腹低血糖

C.评估空腹高血糖

D.监测糖尿病治疗的疗效

E.监测胰腺手术效果
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