计划内事件应至少提前（）个工作日通过系统报告相关事项。
A.1
B.3
C.5
D.10
参考答案：C
介词填空。
1. They help to educate the public about caring _____ the animals.
2. I agree _____ you.
3. It's hard _____ stop riding in cars.
4. I have never heard _____ the woman.
5. She makes model toys _____ old TVs.
6. The walls are made _____ old glass bottles.
7. It's polite to take a few flowers _____ a gift.
8. He was late _____ a business meeting.
气焊铝时，产生的气孔主要是氮气孔。
