赵老师在数学《第一场雪中》时，播放了北方漫天大雪时的视频，让学生感受下雪场景，他运用的教学手段属于()。
A. 实物直观
B. 模像直观
C. 语言直观
D. 虚拟直观
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Observe the output of ‘ls – l’ command, the last 3 bits of the first column represents
A. file type
B. permissions for the file owner
C. permissions for the the group
D. permissions for other users
If chmod 444 fido is executed successfully, then permission of fido is
A. -rwxr-xr-x
B. -rwxr--r--
C. -r--r--r--
D. -r-xr-x—x
The most convenient command or operation to terminate a foreground process (without signal masking) is
A. kill
B. Ctrl+c
C. halt
D. shutdown
About command ‘# mv abc xyz’, which statement is wrong:
A. If abc is a normal file and xyz doesn't exist before, then this command will change the file name abc to xyz.
B. If abc is a normal file and xyz is a directory, this command will move file abc into directory xyz.
C. If abc is a directory and xyz is also a directory, this command will make abc to be the subdirectory of xyz.
D. If abc is a directory and xyz is a normal file, this command will overwrite xyz, i.e. xyz will lost.
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