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

DISTRACTING PREDICATE NOUNS
GRAMMAR
The subject is the center of interest in a sentence, and the predicate
is what provides information about the subject: either describing it
or identifying an action that it performs or that is performed upon
it. (For a more complete description, see "Basic Sentence Structure"
on page 55.)
If the predicate is a description that contains a noun, writers
sometimes mistake this predicate noun for the subject itself. This
will cause errors in agreement if the subject happens to be singular
and the predicate noun plural, or vice versa.
Consider the following two sentences:
Her ongoing grievances are the biggest issue.
The biggest issue~ her ongoing grievances.
In the first example, the subject is the plural grievances: Don't
be decoyed by the singular issue. In the second example, the wording
is turned around so that the reverse is true.
Similarly,
The only deductible item on my tax return~ my travel expenses.
My travel expenses are the only deductible item on my tax return.
Her best feature~ her eyes.
Her eyes are her best feature.
The never-ending crises and tantrums in the office were a nightmare.
The main thing needed ~cooler heads.
The only problem with the house was its creaky floors.
Writers are likelier to focus on the wrong noun if other words
intervene between the subject and the verb. Remember, it is not
proximity that determines which word acts as the subject.
INVERTED SUBJECT-VERB ORDER
In English, the subject usually precedes the verb: Lauren ~a hard
worker; the fox jumps over the dog; his idea was pooh-poohed.
However, this order is reversed in sentences that are constructed
as questions, that open with phrasings such as there were or it is, or
that say what was done before saying who did it. In these situations,
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