钢筋拉伸试验前，首先应在标距两端和中间截面处，测量相互垂直的两个直径，取其平均值分别

若（a-2x）⁵展开式中x²的系数为40，且(a-2x)5=a0+a1x+a2x2+a3x3+a4x4+a5x5．

（1）求(a0+a2+a4)2-(a1+a3+a5)2的值；

（2）求|a₀|+|a₁|+|a₂|+|a₃|+|a₄|+|a₅|的值；

（3）求a₁+2a₂+3a₃+4a₄+5a₅的值．

关于自救器的说法，正确的是（）。

A.矿井下井可以不带自救器 

B.部分人员经矿长允许，可以不带自救器 

C.瓦斯检查员可以不带自救器 

D.入井人员必须随身携带自救器

吃水果的最佳时间（）

A.起床后

B.睡前

C.饭前1小时

D.任何时间

Scientists around the world are racing to learn how to rapidly diagnose, treat and stop the spread of a new, deadly disease. SARS — Severe Acute Respiratory Syndrome — was (1) for the first time in February 2003 in Hanoi, (2) since then has infected more than 1,600 people in 15 countries, killing 63. At this (3) , there are more questions than answers surrounding the disease.

Symptoms start (4) a fever over 100.4 degrees F, chills, headache or body (5) . Within a week, the patient has a dry cough, which might (6) to shortness of breath. In 10% to 200% of cases, patients require (7) ventilation to breathe. About 3.5% die from the disease. Symptoms (8) begin in two to seven days, but some reports suggest it (9) take as long as 10 days. Scientists are close to (10) a lab test to diagnose SARS. In the meantime, it is diagnosed by its symptoms. There is no evidence (11) antibiotics or anti-viral medicines help, (12) doctors can offer only supportive care. Patients with SARS are kept in isolation to reduce the risk of (13) . Scientists aren’t sure yet, but some researchers think it’s a (14) discovered coronavirus, the family of viruses that cause some common colds.

Most cases appear to have been passed (15) droplets expelled when infected patients cough or sneeze. Family members of infected people and medical workers who care for them have been most likely to (16) the illness. But recent developments in Hong Kong suggest that the (17) might spread through air, or that the virus might (18) for two to three hours on doorknobs or other (19) Health experts say it is (20) , though, that sharing an elevator briefly with an infected person would be enough to pass the virus.

20（）

A.probably

B.obviously

C.unlikely

D.clearly

用来渲泄洪水保证水利枢纽的水工建筑物是（）。

A.厂房

B.溢洪道

C.大坝