题干

杂交水稻比常规水稻产量高,土地肥沃的杂交稻比土地贫瘠的杂交稻产量高。引起上述变异的原因

A:都是遗传物质的变化

B:都是环境条件的变化

C:前者是遗传物质的变化,后者是环境条件的变化

D:前者是环境条件的变化,后者是遗传物质的变化

上一题 下一题 0.0难度 选择题 更新时间:2016-04-22 05:30:49

答案(点此获取答案解析)

C

同类题3

阅读理解

    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.

同类题4

收看电视节目不仅可以开阔我们的视野,也是学习课本知识的一种好方法。九年级学生小明在观看新闻节目时就有许多感悟。你知道他从这些新闻事件里体会到了哪些课本里的知识点吗?(每则材料答出两点即可,最多只能答三点)

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