1、Your mother hasn't taught you to use it ,have you（改为has she）?
2、That wasn't a knock at the back door ,was that(改为it)?
3、There is plenty of fuel in the machine ,isn't it(改为there)?
4、Bob told an interesting story to his classmates,did（改为didn't） he?
1、Your mother hasn't taught you to use it ,have you（改为has she）?
2、That wasn't a knock at the back door ,was that(改为it)?
3、There is plenty of fuel in the machine ,isn't it(改为there)?
4、Bob told an interesting story to his classmates,did（改为didn't） he?