通道指示灯：当电流传感器有工作电流时，（）LED点亮。当电流超过上门限或小于下门限时，（）LED点亮，以示告警。
参考答案：绿色；红色
2x2-2x-1=0的解是______，______．
If they had known what was coming next, they _____ their mind. [ ]
A. may change
B. could change
C. must have changed
D. might have changed
