20种氨基酸平均相对分子质量为128，某蛋白质相对分子质量为10 228，在形成该蛋白质分子时脱去水的总量为1548。那么组成该蛋白质的肽链数是(   )

据报告,九江10月9号的空气污染指数为30,那么这天九江的空气质量级别为

用力推课桌的中部，课桌会沿地面滑动，而用同样大小的力推课桌的上部，则课桌可能会倾倒，这说明力的作用效果（　　）

若$\sqrt{x-1}+\sqrt{x+y}=0$  ，则$x^{2005}+y^{2005}$  的值为： （      ）

    Do you want to be a basketball player like Kobe Bryant or Yao Ming? Come to join us! We have many sports clubs: basketball, table tennis, football, volleyball, and more. The price is 5 dollars for each lesson.

    Do you want to join our sports clubs? Please call Mr White. He plays basketball very well. His telephone number is 481-1324. Or you can call Miss Jones at 481-1327. She is our tennis coach. She is good with the students.