—I am really struck by your spoken English. You speak so fluently. Have you been abroad?—Yes. I ____

题干

—I am really struck by your spoken English. You speak so fluently. Have you been abroad?

—Yes. I ______ in London for two years.

A：have stayed

B：stayed

C：had stayed

D：have been staying

上一题下一题 0.0难度选择题更新时间:2019-10-30 12:21:16

A

已知某班学生语文与数学的学业水平测试成绩抽样统计如下表，若抽取学生n人，成绩分为A（优秀）、B（良好）、C（及格）三个等级，设x，y分别表示语文成绩与数学成绩，例如：表中语文成绩为B等级的共有20+18+4=42人，已知x与y均为B等级的概率是0.18．

（Ⅰ）求抽取的学生人数；

（Ⅱ）设该样本中，语文成绩优秀率是30%，求a，b的值；

（Ⅲ）已知a≥10，b≥8，求语文成绩为A等级的总人数比语文成绩为C等级的总人数少的概率．