什么是异温高处作业？
参考答案：
在高度或低温环境下进行的高处作业，称为异温高处作业。
—Do you think we should accept that offer?
—Yes, we should, for we________such bad luck up till now, and time__________out. [ ]
A. have had; is running
B. had; is running
C. have; has been run
D. have had; has been run
设有20个关键码，用起泡排序法对它进行排序，最大的比较次数是______。
A．20
B．200
C．50
D．190
