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?

Piping through cat without -p1 uses the default -p0, which does not strip any directory prefix, causing patch to fail to locate the target files in the kernel source tree.

-p0 does not strip the leading directory component from patch paths, so the patched file paths will not match the actual file locations under /usr/src/linux.

Using > instead of < redirects output to /tmp/foopatch, overwriting or truncating the patch file rather than reading it as input.

The command cd /usr/src/linux; patch -p1 < /tmp/foopatch changes to the kernel source directory and uses patch with -p1 to strip one leading directory component from paths in the patch file, which is the standard convention for kernel patches generated with diff -u. The < operator correctly reads the patch file as input to the patch command.

Running from /root with -p0 means the working directory is wrong and no directory stripping is applied, so patch cannot find the kernel source files to modify.