问题
单项选择题
某人沿着半径为R的圆形轨道从A点运动半圈到达B点时，他的位移大小等于（）
A.0
B.R
C.2R
D.πR
答案
参考答案：C
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某人沿着半径为R的圆形轨道从A点运动半圈到达B点时，他的位移大小等于（）
A.0
B.R
C.2R
D.πR
参考答案：C
| 根据九年级英语上册同步练习unit8《I'll help clean up the city parks》，完成下列任务。 |
| 1. The purpose (目的) of the organization "Animal Helpers" is to help . |
| A. poor people B. old people C. disabled people |
2. What's wrong with Liz Sm ith according to the letter? |
| A. She is unable to see well. B. She is unable to move well. C. She is unable to hear well. |
| 3. How long was Liz's training with the dog at "Animal Helpers"? |
| A. Six weeks. B. Half a year. C. More than a year. |
| 4. Liz Smith wrote the letter to thank Miss Li because she . |
| A. sent some money to her B. gave her a special dog C. donated money to "Animal Helpers" |
| 5. Which of the following is NOT true? |
| A. Lucky can pronounce some English words. B. "Animal Helpers" trains animals like Luc  ky.C. Lucky can fetch some things for disabled people. |