Grammatically Correct: The writer's essential guide to punctuation ...

GRAMMATICALLY CORRECT
Not only the patient but also her family members feel that the nursing
care is excellent.
Not only the students but also the teacher has signed the petition.
Whether the workers or the supervisor was responsible was a matter of
debate.
Whether the tablecloth or the placemats ~on the table is up to you.
Note that constructions that include a plural subject but use a
singular verb may sound awkward. A simple solution is to switch
the components around: Either Zeke's sister or his parents are
going to attend; Not only the teacher but also the students have
signed the petition. Or avoid the issue by using a verb form that
doesn't change with number: Either Zeke's parents or his sister
will attend; Not only the students but also the teacher signed the
petition.
DISTRACTING PARENTHETICAL NOUNS
When a subject is followed by a phrase that refers to another entity,
writers sometimes mistake this entity for the second part of a compound
subject. Consider the following sentences:
Theodora and her daughter are taking classes in Bulgarian.
Theodora, as well as her daughter,~ taking classes in Bulgarian.
The first example contains a compound subject, Theodora and
her daughter, and hence takes a plural verb. The second one contains
a singular subject, Theodora, followed by a parenthetical
phrase that refers to Theodora's daughter but is not part of the
subject. Thus, Theodora, as well as her daughter, are taking
classes in Bulgarian would be incorrect. If a parenthetical phrase
is taken out, the sentence should still read grammatically. It is
obvious that you would not say Theodora are taking classes in
Bulgarian.
Similarly,
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His chronic tardiness, as well as his negative attitude, disrupts the class.
The professor, together with her graduate students, was just entering
the building.
The new workload, on top of my other duties, ~ unreasonable.