What single command (no options or arguments) can be used to fully extract a file called abc.tar.bz2? )

`gzip` is a compression utility specifically for `.gz` files and cannot extract `.tar.bz2` files.

`gunzip` is a decompression utility specifically for `.gz` files and cannot extract `.tar.bz2` files.

The `tar` command is capable of handling both the archiving (tar) and the decompression (bz2) aspects of a `.tar.bz2` file. Modern `tar` implementations often auto-detect the compression type (like bzip2) and perform decompression automatically when extracting, making it the single command to fully extract such files.

`bz2unzip` is not a standard Unix/Linux command; the standard command is `bunzip2` or `bzip2 -d`, which only decompresses the `.bz2` part, not extracts the `.tar` archive.