人参皂苷Re是

A:螺旋甾烷醇型 B:达玛烷型 C:齐墩果烷型 D:乌苏烷型 E:羽扇豆烷型

Re用来表示（）。

A:炉渣碱度 B:碱土金属 C:稀土金属 D:电阻

Re准数的单位是（）。

A:m B:m/s C:m3/kg D:没有单位

Re没有单位。

人参皂苷Re是

A:螺旋甾烷醇型 B:达玛烷型 C:齐墩果烷型 D:乌索烷型 E:羽扇豆烷型

有压圆管恒定流，若断面1的直径是其下游断面2的直径的二倍，则断面1的雷诺数Rei与断面2的雷诺数Re₂的关系是：

A:Re₁=Re₂ B:Re₁=0.5Re₂ C:Re₁=1.5Re₂ D:Re₁=2Re₂

Digital photography is still new enough that most of us have yet to form an opinion about it, (1) develop a point of view. But this bash’ t stopped many film and computer fans from agreeing (2) the early conventional wisdom about digital cameras—they’ re nea (3) for you But they’re not suitable for everyday picture taking.
The fans are wrong: Moro than anything else, digital cameras are radically (4) what photography means and what it can be. The venerable medium of photography (5) we know it is beginning to seem out of (6) with the way we live. In our computer and camcorder (7) saving pictures as digital (8) and watching them on TV is no less practical—and in many ways more (9) than fumbling with rolls of film that must be sent off to be (10) .
Paper is also terribly (11) . Pictures that are incorrectly framed, (12) ,or lighted are nonetheless committed to film and ultimately processed into prints.
The digital medium changes the (13) . Still images that are (14) digitally can immediately be shown on a computer (15) , a TV screen, or a small liquid -crystal display (LCD) built fight into the camera. And since the points of light that (16) an image are saved as a series of digital bits in electronic memory, (17) being permanently etched onto film, they can be erased, retouched, and transmitted (18) .
What’s it like to (19) with one of these digital cameras It’s a little like a first date--exciting, confusing and fraught with (20) .

A:re-explaining B:rearranging C:re-exposing D:redefining

“合同号”：RE01。

流体流动的判据为 Re准数 。对于直管来讲，如 下说法哪个正确 ( )

A:Re> 2000为层流 B:Re<4000为层流 C:Re< 2000为湍流 D:Re> 4000为湍流