单选题 The upper atmosphere is believed to consist of a number of roughly concentric layers, which include the troposphere (???) and stratosphere (???).
  • A. plainly
  • B. repeatedly
  • C. nearly
  • D. changeably


【正确答案】 C
【答案解析】[解析] roughly：大概地、粗略地，和nearly(几乎、差不多)意思相近；plainly：明白地；repeatedly：反复地、再三地；changeably：易变地、常变地。