防止苯并（a）芘危害的措施是什么？

人类最后发现的一块大陆是（　　）

A．澳大利亚大陆

B．非洲大陆

C．南极洲大陆

D．美洲大陆

人工钨丝灯光源的特点是（）

A.色温低

B.寿命长

C.耗电少

D.便于观察布光效果

用水平力F拉一物体，使物体在水平地面上由静止开始做匀加速直线运动，t₁时刻撤去拉力F，物体做匀减速直线运动，到t₂时刻停止．其速度—时间图象如图所示，且＞，若拉力F做的功为W₁，平均功率为P₁；物体克服摩擦阻力F_f做的功为W₂，平均功率为P₂，则下列选项正确的是

A．W₁＞W₂；F＝2F_f

B．W₁= W₂F＞2F_f

C．P₁﹤P₂; F＞2F_f

D．P₁＝P₂; F＝2F_f

阅读表达。

阅读下面短文并回答问题,然后将答案写到答题卡相应的位置上(请注意问题后的词数要求)。

 ［l］Internet use appears to cause a decline in psychological well-being, according to research at

Carnegie Mellon University.

   [2] Even people who spent just a few hours a week on the Internet experienced more depression and

loneliness than  those who logged on

less frequently, the two-year study showed. And it wasn't that people who were already feeling bad spent more time on the Internet, but that using the Internet actually appeared to cause the bad feelings.

    [3]Researchers are puzzling over the results, which were       .They expected that the Internet would

prove socially healthier than television, since the Internet allows users to choose their information and to

communicate with others freely.

    [4]The fact that Internet use reduces time available for family and friends may account for the drop in

well-being. Faceless, bodiless "virtual" communication may be less psychologically satisfying than actual

conversation, and the relationships formed through it may be shallower. Another possibility is that

exposure to the wider world via the Internet makes users less satisfied with their lives.

    [5] "But it's important to remember this is not about the technology, it's about how it is used," says

psychologist Christine Riley of Intel, one of the study's sponsors. "In really points to the need for

considering social factors in terms of how you design applications and servises for technology."

1.What's the main idea of the text?(no more than 10 words)

______________________________________________________________________________

2.What is the meaning of the underlined phrase "logged on"in Paragraph 2?(no more than 3 words)

______________________________________________________________________________

3. Fill in the blank in Paragraph 3 with proper words.(no more than 5 words)

______________________________________________________________________________

4. Complete the following statement with words from Paragraph 4.(2 words)

    Experiencing the          online may cause Internet users to feel their real lives unsatisfactory.

5. Translate the underlined sentence in Paragraph 5 into Chinese.

_______________________________________________________________________________

HQ2150³2³0.6电缆直通接头铅套管规格为（）。

A.30³300

B.40³300

C.50³300

D.50³400