题干

观察植物细胞的质壁分离与复原、叶绿体中色素的提取和分离、温度对酶活性的影响、DNA 的粗提取与鉴定,这四个实验的共同点是                                  (   )

A:实验材料都要保持生物活性

B:实验设计中都需有对照

C:实验过程中均要加热

D:实验结果都有颜色变化

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D

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    A telescope, called Gaia, is being designed by astronomers in Europe, and it couldn't be more different from Pan-STARRS, which is another telescope being designed. While Pan-STARRS will be looking for asteroids (小行星) and comets headed for Earth, Gaia will be looking at our entire galaxy (银河系).

    Gaia is designed to draw a map of the Milky Way, our home galaxy. Just as a map of your town gives you a picture of where things are located, Gaia's map of the galaxy will tell astronomers where the stars are. Over five years, Gaia will observe (观察) about a billion stars and other objects in our galaxy. Each object will be observed about 70 times.

    Gaia will be sent into space connected to a rocket. It contains two telescopes, each focused at a different angle (角度). These two telescopes act like Gaia's “eyes”. The reason why humans can see things in 3D is that we have two eyes focused on the same object, at slightly different angles. By using two telescopes like eyes, Gaia can produce the first 3D map of the positions of the stars it views.

    Gaia, which is to be sent into space, will be a powerful telescope. If you were to use it on Earth, for example, you could stand 600 miles away from your best friends and still get a clear picture of their hair.

    Gaia is one of more than a dozen telescopes being designed by scientists right now. The next generation of telescopes will reveal new parts of our universe that will seem surprising. The universe, with all its planets, stars and other strange objects, is a puzzle with pieces that we can see by using powerful telescopes.