政府采购的当事人不包括( )。 A．采购人 B．供应商 C．采购代理机构 D

勘察工作通常包括（）与位置的选择隧道洞口与洞身的勘察。

下列疾病哪一项是缺乏维生素C所引起的（　　）

A．佝偻病

B．坏血病

C．糖尿病

D．肝炎

The British people are among the world’s greatest readers of newspapers．It’s been the custom ever since most people could read．

But why do people want to do nothing but read while traveling to work in a train? Perhaps they are tired, or else they sit behind a newspaper to shut themselves off from the world．All the same, most men would notice a woman struggling with a heavy case and jump up to help her and a pretty girl sitting opposite wouldn’t escape their attention either．In this case a paper is useful because they can have a good look at her from behind it without her knowing．Perhaps they do nothing but read．There are stories of girls and young men who met in the rush hours, got married, and went on traveling in the same train hand in hand．

小题1:The main idea of this passage is that______．

A．people in Britain are great newspaper readers

B．why people read newspaper when they travel by train

C．people do nothing but read in a train

D．when people go to work in a train, they do different things小题2:According to this passage, reading newspaper______．

A．is a custom just among men who can read

B．is something the British do only traveling in a train

C．is a daily activity most people enjoy

D．can help people in many ways小题3:A man might be reading a newspaper in a train for the following reasons except that ______．

A．he is trying to get some business news

B．he wants to have a rest

C．he hopes to escape the attention of a pretty girl

D．he doesn’t want to talk with other people around him小题4:The writer said that most men in the train would help a woman struggling with a heavy thing．The implication(含义) is that ______．

A．It is interesting for a man to help a woman in trouble

B．it is considered a man’s duty to offer help to a woman in need

C．the woman is too weak to carry a heavy case

D．men are often more interested in other things than reading newspapers, especially when women are in trouble

如图所示，一固定直杆AB长为L＝2m，与竖直方向的夹角为θ＝53°，一质量为m＝4kg、电荷量为q＝＋3×10^－5C的小球套在直杆上，球与杆间的动摩擦因数为μ＝0.5。直杆所在处空间有水平向右的匀强电场，场强为E＝10⁶N/C，求：

（1）小球静止起从杆的最高点A滑到最低点B时的速度大小v₁；

（2）若杆与竖直方向的夹角换成不同的值，小球滑到B时的速度也会不同，为使小球滑到杆的B端时的速度最大，某同学认为应使杆沿竖直方向放置，因为这样重力做的功最多。你认为是否正确，若认为是正确的，请求出此最大速度v₂，若认为不正确，请说明理由并求出此时杆与竖直方向的夹角及此最大速度v₂。

蜗杆传动的失效形式大多发生在（）。

A.蜗杆

B.蜗轮

C.蜗杆和蜗轮

D.轴