Better sentence-writing in 30 minutes a day - Dianna Campbell 1995

Three important points
Subject-verb agreement
Revising at the word level

There are three important points about subject-verb agreement that everyone should know. We’ll look at each one before you begin the more difficult exercises.

1. Using And and Or between Key Words in the Subject

You probably already know that two singular words joined with and form a plural subject. But you should also know that two singular words joined with or form a singular subject. Study these correct examples:

2. Using Prepositional Phrases in the Subject

Remember when you worked with prepositional phrases in Chapter 1? The key word in the subject is never within a prepositional phrase, and the key word in the subject is, of course, the word with which the verb must agree. So you have to be careful to set off any prepositional phrases that appear within the complete subject of a sentence.

Study these correct examples:

In (a), the word festivals is the key word in the subject, and because it is plural, it agrees with are. But in (b), the word festivals is not the key word in thesubject. Why not? It’s not the key word because it’s in a prepositional phrase— of rock and roll festivals. (The preposition is of.) A prepositional phrase modifies the subject, but it never contains the subject.

In (b), the key word in the subject is history, and because history is a singular word, it agrees with the verb is.

3. Using Delayed Subjects

There are two kinds of sentences that have delayed subjects. A subject is called “delayed” when it follows the verb.

One kind of sentence with a delayed subject begins with the word there or here. If a sentence begins with either word, you have to look beyond the verb to find the real subject—the word with which the verb must agree. Study these correct examples:

Think of the words there and here as empty sentence starters. They’re not the subjects in any of the preceding four sentences. They’re sort of placeholders that indicate where the subject word would normally be.

The other kind of sentence with a delayed subject is a question. In the following sentences, the question word acts in the same way as there or here. Study these correct examples: