Rickooreo
Can you please shed some light on how to understand inverted verb. I though has will refer to part and hence should be singular.
The type of inverted verb structure that you see here involves a verb that...
... appears in the
second half of a parallel structure along with its subject; (i.e., the two parallel parts are clauses that each contain a subject + verb)
... is a compound that contains a
helping verb.
Here are the basic ideas that govern these structures.
• If the subject of that latter verb is just a plain noun, or a noun followed only by a short modifier, then typical stylistic conventions
discourage inverting the helping verb and root verb.
e.g.,
My grandmother tends to collect far fewer souvenirs on trips abroad than my grandfather does.
You CAN write "...than does my grandfather"—but there's no actual reason to perform this inversion here, so good writers typically won't invert the verb.
BUT
• If the subject of that latter verb is
followed by a long modifier (or long series of modifiers), then it's more common to
invert the helping verb and subject. (Only the helping verb appears in this second part; the core verb is the same as in the first part and thus needn't be repeated. If there are two different core verbs, there's no possible inverted structure of this type.)
e.g.,
My grandmother tends to collect far fewer souvenirs on trips abroad than does my grandfather, who will usually return home with musical instruments, clothing, and gifts for the whole family in extra luggage that he had to purchase to get everything home.
If you don't see the rationale for inverting this verb, try NOT inverting it—which will mean placing "does" all the way over to the right, after that whole gigantic modifier—and you'll see how hard it is to understand that sentence on one read-through. That's the justification for verb inversion.