Neither, either or, etc.?
When “either A or B”, “neither A nor B”, “not A but B”, “not only A but also B” and “both A and B” are the subject of the sentence, do you use the verb with the plural or singular form?
In my opinion, "B" determines the form of the verb when the subject of the sentence is "either A or B," "neither A nor B," "not A, but B," and "not only A, but also B." Furthermore, I believe the plural form should be used when the subject of the sentence is "both A and B." Is my opinion correct?
I assume that your question is so meant that A and B are both singular forms. Otherwise, it should be clear how to proceed.
In my German grammar of Hentschel and Weydt there is an elongate chapter on congruence, which covers some of these cases. Unfortunately, in many cases the authors conclude that both are possible and do not justify it.
So I can only answer this from my language feeling, and that says: Use plural, except if there is a clear argument for singular.
Hentschel and Weydt mention another, somewhat ancient design, namely the preposition and. You give as an example Director Meier and wife are expected to be tea. As you can see, they think both variants are correct, and I think that in turn is untenable, because the spouse is in the Dativ and therefore cannot be counted as a subject. In my frustration I searched for evidence in the literature and find there as expected Singular: which, unfortunately, considers this unfortunate and many others to be truthful (Goethe, Großkophta) or the often overcrowded jewellery box along with the downcrowded carpet […] (Grillparzer, monastery near Sendomir).
related to this question constructio ad sensum, that is, the use of a plural verb for a quantity, even if it is expressed by a singular substituent: A lot of people came/ came to the summer break. I have never liked this construction and almost always use singular for the verb, but the plural is widely used in such sentences. Goethe agrees to me, though: Like a great crowd […] spread over Menin, Comines, Verwich, Lille (Egmont).