I was giving an opinion based on what I had read in a grammar textbook. This is what I saw recently on a grammar web page:
The conjunction or does not conjoin (as and does): when nor or or is used the subject closer to the verb determines the number of the verb. Whether the subject comes before or after the verb doesn't matter; the proximity determines the number.
Either my father or my brothers are going to sell the house.
Neither my brothers nor my father is going to sell the house.
Are either my brothers or my father responsible?
Is either my father or my brothers responsible?
However, here is an opinion at another grammar web page on this grammar point:
Plural Verb with a Plural Element
If the pairings either/or or neither/nor form part of the subject of a verb and at least one of the elements is plural, then the verb must be plural too.
Neither the lawyer nor the detectives are able to follow the sequence
of events. ;-)
"lawyer" (singular - i.e., one person), "detectives" (plural - i.e., more than
one person), "are" (plural - i.e., not "is")
There were neither cakes nor ice-cream at the party. ;-)
Neither the firemen nor the policemen know him. ;-) (i.e., not "knows")
Either the budgies or the cat has to go. :-(
Not all grammar conventions agree with the ruling above. In fact, there is notable leniency on whether to use a plural or singular verb when one of the elements is plural. Under 'the proximity rule', the verb is governed by the element nearest to it.
Either crumpets or cake is sufficient.
( :-( under standard convention; should be "are sufficient")
( ;-) under the proximity rule - "cake" governs "is" because it is the nearest element.)
There was neither ice-cream nor chocolates at the party.
( :-( under standard convention; should be "were")
( ;-) under the proximity rule - "ice-cream" governs "was" because it is the nearest element.)
I personally feel that if this grammar point is something that is usually asked from your students for their tests, it may be useful to find out what answer is expected from them.