Which of the following commands displays the contents of a gzip compressed tar archive?

`gzip archive.tgz` would attempt to re-compress an already compressed file or incorrectly handle the pipe, and `xvf -` would extract, not just list, if it even received input.

The command `tar ztf archive.tgz` efficiently displays the table of contents (`t`) of a specified archive file (`f`) that has been compressed with gzip (`z`), without extracting its contents.

`gzip -d archive.tgz` without `-c` decompresses to a file named `archive.tar` (or similar) in the current directory and does not send output to stdout for piping; therefore, this command sequence is functionally incorrect for piping.

`tar cf archive.tgz` is used to create (`c`) a tar archive (`f`) from files, not to display the contents of an existing one.