Which command would you use to apply a diff file to an original?

Which command would you use to apply a diff file to an original?

A.
patch > diff-file

B.
patch < diff-file

C.
patch << diff-file

D.
cat diff-file >> kernel

E.
cat diff-file << kernel

Explanation:

From the man pages:
SYNOPSIS
patch [options] [originalfile [patchfile]]
but usually just
patch -pnum < patchfile