电力系统发生振荡时，（）不会发生误动。
A.分相电流差动保护
B.距离保护
C.电流速断保护
D.以上都不正确
参考答案：A
We must keep a positive attitude toward the future ________ we may encounter some difficulties.[ ]
A. however
B. as if
C. even if
D. since
肺野
