题干

下图表示细胞分裂的不同时期与每条染色体DNA含量变化的关系。下列对图示的分析,不正确的是

A:DNA合成的抑制物能作用于AB段

B:为获得多倍体,使用秋水仙素溶液作用于BC段

C:DE段的每条染色体含有一个DNA分子

D:该图示表示细胞有丝分裂过程中染色体的变化

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D

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    Flying devices called drones(无人机) may be one of the most important technologies of the future.

    The number of jobs for people who know how to design, build and control them is increasing. Because of this increase, several U.S. universities have started offering degrees in unmanned aircraft systems, or UAS.

    One of these universities is the University of Washington in Seattle. Ward Handley is seeking a master's degree in UAS at the university. When the drone program first began, he did not think it was a good idea. “Drones can be used to invade privacy(侵犯隐私).” He said. But later, Handley changed his opinion. He said, “I think there are good enough purposes for them.”

    The FAA (the part of the U.S. government that controls air travel and traffic) is creating new rules to control the use of drones, however. A new law requires drone owners to register(登记) their drones. People who do not register their drones could face fines of up to US$20,000.

    The new rules may also present problems for students. One problem is finding a legal place to fly.

    Students at Blue Mountain Community College fly inside the college gym. In Seattle, University of Washington students test their drones in a big room.

    Christopher Lum, a scientist at the University of Washington, helps students explore how drones can safely share the sky with regular aircraft. Lum explained why they test drones inside a building, “We need to register our aircraft and get permission to fly outside. That process can take months.”

    At this time, Kansas State University is the only school with permission to offer unmanned aircraft flight classes to students outside. The FAA selected Kansas State University and 15 other universities to be part of a national research group.

    Lum and some of his students recently moved their research to Australia. Australia has fewer rules limiting drones. A professor at Western Washington University also took his department's drones to Canada for the same reason.