求如图所示的交变电流的有效值，其中每个周期的后半周期的图象为半个周期的正弦曲线（

阅读理解。

    The Italian island of Sardinia recently lost its oldest person. Family members say Antonio Todde died in

his sleep early this month. Mr Todde was 112 years old. He was less than three weeks away from his 113th

birthday. Record-keeping experts say he was the world's oldest man.

     His long life and that of other very old Sardinians are the subjects of a scientific project (项目) called

Akea. Luca Deiana of Sassari University is directing (指导) the study. He says the name Akea comes from

a traditional greeting (问候) on Sardinia. It means "health and life for 100 years." Professor Deiana and his

team started to collect information for the study in 1997. They identified (确定)) more than 220 Sardinians

who were centenarians-100 years old or older. His team needed three documents to make sure a person's

age. They were a government (政府) birth record, a church record and a statement (声明) by a close family

member.

     The Akea study has produced two major findings. The first is Sardinia's extremely high number of

centenarians. The island has about 135 centenarians for every one million people. In other Western countries,

the average (平均数) is about seventy-five centenarians for every one million people. The second major

finding is an unusual rate (率) of female (女性) to male (男性) centenarians. Sardinia has two women

centenarians for every male centenarian. In central Sardinia there are the same numbers of female and male

centenarians.

     Studies in other parts of the world have shown a much higher percentage (百分比) of female centenarians.

The Akea study collected information about the health and food of about 140 of the centenarians. About

ninety percent of those in the study also agreed to provide blood (血) for scientific testing. The study team

hopes to identify genetic (基因) material in the blood that can be linked to successful aging. Study leaders

say there is no single reason why people on Sardinia live so long. They believe the answer is a combination

(组合) of genetic and environmental conditions (条件).

1. Centenarians are people who are ______ years old. [ ]

A．200

B．100

C．300

D．400

2. Akea is a scientific project about ______.[ ]

A．Mr Todde's death

B．the long life of Sardinians

C．Sassari university

D．Professor Deiana

3. What is the general idea of the third paragraph? [ ]

A．Sardinia has a large number of centenarians.

B．An unusual rate of female to male centenarians.

C．Two major findings of the Akea study.

D．Sardinia has equal numbers of female and male centenarians.

4. Why do Sardinians live so long according to the study? [ ]

A．Because the environment on Sardinia is very good.

B．Because they have special genetic material in their blood.

C．Because they have a glass of wine every day.

D．Because they enjoy special genetic and environmental conditions.

小刚与同学谈话，2009年国家最高科技成就获得者谷超豪教授，是一名数学家。他历任复旦大学副校长，中国科技大学校长。其研究成果“规范场数学结构。”获全国科学大会奖，本人获该年度最高科技奖，奖金500万元。

（1）小刚有些困惑，谷超豪教授研究几个数字有没有价值？怎样看待他的奖金和荣誉？

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（2）我们今天的学习与我们的人生价值有什么关系？

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（3）小刚与同学讨论后，决心要让自己的生命更精彩。你想他打算怎样做呢？

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道氏理论的创始人也是道-琼斯平均指数的创立人。( )

润滑的作用是减少摩擦和磨损、（）等。

A、散热

B、防腐

C、减震

D、以上三点

如何用径向方根求积仪，拉生产不满24小时的静差压格数？