以下备份类型中最耗时间的是______。
A．完全备份
B．差异备份
C．事务日志备份
D．文件和文件组备份
参考答案：D
He focused on his test papers,________never________the same mistakes.[ ]
A. determined; to repeat
B. being determined; to repeat
C. determined; repeating
D. determining; repeating
下列各题中计算结果正确的是[ ]
A．2x+3y=5xy
B．5a2﹣3a2=2
C．4a2b﹣5ab2=﹣ab
D．x2+x2=2x2
