闸阀是油库中最常用的阀门之一，下面内容中哪一个不属于闸阀的特点（） A.流体阻力小

关于重症肌无力的主要临床表现下列描述正确的是（）

A.横纹肌、平滑肌均可受累

B.可逆性的受累骨骼肌易疲劳，在短时休息或应用抗胆碱酯酶药物治疗后好转

C.不可逆的受累骨骼肌易疲劳

D.脑神经支配肌肉的无力多于脊神经支配的肌肉

E.病情波动

Why is a full moon, yellower and bigger when it is coming up than when it is higher in the sky?

That's a good question about something that we all can see. Let's talk about the moon's color first.

We see the moon only because of the sunlight that falls on it and is reflected. Actually, the moon is not a very good reflector, because its surface is all rocks and dirt. We see it in almost its true color when it is high in the sky.

When the moon first comes up, its light reaches our eyes after an extra-long path through the atmosphere (大气). There are lots of particles (微粒) scattering (分散) light in that long path. Blue light is scattered more than other colors, which means that it doesn't reach your eyes. The light that is left over looks yellow to your eye.

Now about the other question—why the moon seems to change in size. That's more complicated. It's not an effect of the atmosphere, the way color is; it's not caused by something fooling your eyes. It seems, instead, to be caused by something that fools your brain—an illusion(错觉).

Here's a drawing that creates an illusion. The two cones(圆锥体) are really the same size. But the rest of the drawing makes the right-hand cone seem farther away. Your brain knows that faraway objects are really larger than they look. It decides that the right-hand cone must be larger because it seems to be farther away.

Similarly, when you see the moon just come up over a line of trees or houses—or whatever makes the horizon(地平线)—it may be that your brain decides that the moon must be larger because it seems to be farther away.

小题1:The moon doesn't reflect the sunlight very well because________________.

A．it is high in the sky

B．its surface is rough

C．its surface is white

D．it isn't a good reflector小题2:Which statement is true according to the passage?

A．In the course of its rising, the moon is getting smaller and smaller

B．The size of the moon is more complicated than its color

C．The atmosphere has the same effect on the moon's size as on its color

D．The change in the moon's size is caused by an illusion while that in its color is caused by the atmosphere小题3:After reading this passage, you can possibly answer one of the following questions. Which one? ______.

A．Why is the sun bigger when it rises over the horizon?

B．Why does the sun look bigger when it rises over the horizon?

C．Why does the sun look golden?

D．Why does the sun rise in the east?小题4:Who do you think probably wrote this passage?________.

A．A novelist

B．A reporter

C．A science editor

D．An English teacher．

双气囊三腔管每次放气时间为（）

A.5～10分钟

B.10～15分钟

C.15～30分钟

D.30～60分钟

E.60～120分钟

使用者在占有某块土地时，土地只能提供现时的纯收益。 ( )

限操员证书适用于（）海区航行的船舶。

A、A1

B、A1，A2

C、A3.A4

D、全球