S7-300PLC通电后，CPU面板上“BF”指示灯亮，表示（）。
A. 程序出错
B. 通信接口总线故障
C. 系统错误
D. 输入输出模块故障
查看答案
What is the main reason that the Climate Train group traveled by land?
A. To make less pollution
B. To save money
C. to learn about other cultures
Was the Climate Train group happy that they chose to travel by land?
A. no, They will take a plane next time.
B. Yes. They were happy, though it was sometimes difficult.
C. Yes. They were happy, though it was an easy way to travel.
What is the most important thing the Climate Train group came to understand on their journey?
A. Pollution doesn't stop at borders. An international conference is necessary to sove the problem.
B. Russian trains have fun restaurant cars.
C. It's important to speak many languages so that you can talk with lots of people.
What do the Climate Train travelers hope that other people will do?
A. Spend more time at borders.
B. Travel by land and sea instead of by air.
C. Go to more international climate conferences.
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