什么情况下程序会发生中断嵌套？
参考答案：必须在中断服务程序中打开中断，程序才会发生中断嵌套。
若-x2m-1ym与8x3yn-1是同类项，则代数式（m-n）2007的值是______．
Had it not been for the fact that she ____ in the accident, she ____ in the race．
A．got injured; would have competed
B．had got injured; would compete
C．would be injured; would have competed
D．should be injured; would compete
