单项选择题

案例分析题 Total enrollment in higher education institutions, by control
and type of institution: Fall 1972-95

A bag contains 3 red, 4 white, and 5 blue marbles. Jason begins removing marbles from the bag at random, one at a time. What is the least number of marbles he must remove to be sure that he has at least one of each color （）

A.3
B.6
C.8
D.10
E.12

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单项选择题

In 1995 the number of students enrolled in public institutions of higher education was approximately how many times the number of students enrolled in private institutions of higher education （）

A.2
B.2.5
C.3
D.3.5
E.4

单项选择题

Human fascination with space began hundreds of years ago. That interest has not waned, and today, the Hubble Telescope orbits 375 miles above Earth, working nonstop to unlock the secrets of the universe. The Hubble uses state-of-the-art instruments to provide amazing views of the universe that cannot be matched by ground-based telescopes. The reason for this is that, from the ground, we look at stars and other objects in space through Earth’s atmosphere. Our atmosphere is full of clouds, dust, and pollution, which cause everything we see to shimmer and shake. This effect creates difficulty for scientists on the ground to make steady, accurate measurements of objects moving in space. With assistance from the Hubble Telescope, astronomers can pinpoint the location of faraway stars and galaxies, and measure the speeds and distances of astronomical objects with far greater precision. Astronomers may even one day tell us exactly when the universe began. The author suggests that steady,accurate measurenebts can be difficult to attain because.（）

A.scientists frequently introduce unnecessary comolications to simple situations.
B.Earth-based telescopes are insufficiently peecise due to atmospheric dust and pollution.
C.due to Earth's constant rotation,it is nearly impossible to pinpointexact distances in outer space.
D.most telescopes require regular repairmissions when their cameras aren't functioning properly.
E.astronomers are not yet able to tell us exactly when the universe began.