"抑郁发作"的特点不包括（）。
A.思维缓慢
B.思维中断
C.情绪低落
D.语言动作减少和迟缓
参考答案：B
Go on with your English study. _____ is difficult if you put your heart into it. [ ]
A. Anything
B. Something
C. Nothing
UNIX的文件备份策略有哪些？
