站控室人机界面可以自动触发（）级别的关断。
A.1
B.2
C.3
D.4
参考答案：A
数据2500000用科学记数法表示为
A．25×105
B．2.5×105
C．2.5×106
D．2.5×107
If the sun’s rays were entirely _______, there would be dramatic changes in the climate on the earth, and the result could be disastrous to the human race. [ ]
A. covered out
B. broken out
C. blocked out
D. left out
