which of the following commands should be used to apply the patch /tmp/foopatch?

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?

A.
cat /tmp/foopatch | patch -p0

B.
cd /usr/src/linux; patch -p1 < /tmp/foopatch

C.
cd /usr/src/linux; cat /tmp/foopatch | patch -p0

D.
cd /usr/src/linux; patch -p1 > /tmp/foopatch

E.
cd /usr/src/linux; cat /tmp/foopatch | patch

Explanation:
patch takes a patch file patchfile containing a difference listing produced by the diff program and applies those differences to one or more original files, producing patched versions. Normally the patched versions are put in place of the originals.
Answer D is correct because first changes the directory and running patch command by taking input from the /tmp/foopatch.