题干

在某水生生态系统中,分布有水鸟、藻类、芦苇等动植物,某些水鸟具有秋季迁移的习性.下列叙述错误的是(  )

A:该水生生态系统的物种数量随季节而发生变化

B:减少芦苇和藻类后,输入该水生生态系统的能量维持不变

C:藻类和芦苇等生产者固定的能量是流经该生态系统的总能量

D:该水生生态系统动植物残体被微生物分解后可产生含氮化合物

上一题 下一题 0.0难度 选择题 更新时间:2019-05-06 01:50:26

答案(点此获取答案解析)

B

同类题2

      In the past, going to a piano teacher was the only way to learn how to play the piano. You could have one lesson a week. If you didn't have private(个人的) lessons, you could still learn piano, but you would have to learn it by yourself. This was easy for some, but very difficult for most. However, with technology as it is today, there is at last another way that you can take piano lessons. You can take an online course.
    An online course can save you lots of money. If a private lesson costs 30 or 40 dollars per week, just think about how quickly that adds up. You can take a complete online course in piano by spending a small part of the money that you would pay for taking weeks of private lessons. Also, private lessons are only usually one hour per week. If you have questions during the rest of the week, or if you forget something that your teacher said, you will have to wait for your next lesson to continue your learning. However, online piano courses are quite different.
     With an online piano course, you can work at your own pace(进度). You can also take as many lessons per week as you'd want, or go back and listen to your last lesson if you have forgotten anything. Most adults who want to learn how to play the piano enjoy being able to go back and listen to lessons they watched before. It can give you a good idea of what you were doing right, what you were doing wrong, and what you should be doing before the next lesson.
    Of course, if you need someone to sit beside you and give you instant feedback(及时反馈) while you are playing, you are not suggested to choose an online course. But most adult learners think they can get their own type of feedback by watching the course again and again.