旅行社在经营活动中要遵循______、______、______、______的原则。
参考答案：自愿 平等 公平 诚实信用
_______ I have a lot of housework to do, I still finish my homework on time. [ ]
A. Unless
B. If
C. Although
D. So that
避雷器在1.05倍持续运行电压下的局部放电量应不大于（）PC。
A.10
B.30
C.50
D.100
