If the current directory is /root and the kernel source is located in /usr/src/linux, which of the following commands should be used to apply the patch /tmp/foopatch?

`patch` without `-p` might fail due to incorrect path matching, and piping `cat` output is less direct than input redirection.

`patch -p0` would expect file paths in the patch file to be relative to the current directory *without* stripping any directory components, which is less common for kernel patches.

`patch -p1 > /tmp/foopatch` would attempt to write the *output* of the `patch` command to `/tmp/foopatch`, not apply the patch from it.

D is correct because `cd /usr/src/linux` changes to the directory where the patch needs to be applied, and `patch -p1 < /tmp/foopatch` then applies the patch. The `-p1` option tells `patch` to strip one leading directory component from the file paths in the patch file, which is common for patches generated from a `diff -uprN` command, and `< /tmp/foopatch` redirects the patch file content as input to the `patch` command.

Applying the patch from `/root` without changing directory would likely result in "File not found" errors for the paths within the patch.