Modifiers
The functions of DO, IO, predicative complement, and oblique complement all have one common
property: they are all selected by the verb, and we view them as being present to ‘complement’
the verb to form a legitimate VP. Hence, these are called complements (COMPS), and
typically they cannot be omitted.
Unlike these COMPS, there are expressions which do not complement the predicate in the
same way, and which are truly optional: