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

GRAMMATICALLY CORRECT
When the element closest to the verb is singular, some writers
mistakenly make the verb agree with just that part. Consider the
following examples:
Her understanding and attention span has improved greatly.
The verb should be have.
Whether a relationship between these events actually exists and if so
whether it is causal remains to be shown.
The verb should be remain.
Desktop publishing may not yield the same quality achieved by
traditional typesetting, but its cost-effectiveness and the control that it
offers to editors makes it attractive to many publishers.
The verb should be make.
Note that it is particularly easy to miss the fact that there is more
than one subject if the elements are long, complex or abstract.
Exceptions
• If two elements refer to the same entity, treat them as if they
constitute a single subject.
Rum and Coke was his preferred drink.
[rum and Coke combine to form one beverage]
The president and CEO expects to attend.
[president and CEO describe the same person]
Drinking and driving ~a crime.
[drinking and driving are not crimes in isolation, only in combination]
Sometimes the status may be a matter of interpretation:
Plucking and cleaning a chicken was an unpleasant task for many of our
grandmothers.
Calculating and plotting the points on a graph~ the most time­
consuming part of the analysis.
In each of these sentences, the closely related actions may be
considered to function as a single activity. It would be grammatical
to use plural verbs and change the descriptions to tasks and parts,
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