根据《特大安全事故行政责任追究规定》，特大安全事故发生后，事故调查工作应当自事故发生之日起____

UNIX系统中，关于cp命令，下列()是错误的。

A．cp filel file2

B．cp filel file2 /tmp

C．cp-r filel file2

D．cp-r /tmp/mytmp

把文件file1和file2合并成file3的命令是 ()

A.Explain that the files never existed in the first place.

B.Explain that during a Migration install the /tmp filesystem is overwritten.

C.Explain that after a Migration install, all system filesystems will be empty.

D.Explain that /tmp is temporary storage and files are automatically removed every 30 days.

A．cp file1+file2 file3

B．cat file1 file2 >file3

C．mv file file3

D．join file1 file2 >file3