An agreement error is the faulty combination of a singular and a plural. A subject-verb agreement error occurs between subjects and their verbs. The rule is to use a singular verb with a singular subject and a plural verb with a plural subject. The key to spotting errors of subject-verb agreement is identifying the subject correctly. Often, the sentences will try to mislead you by separating the subject and verb:
E.g. The sound of birds singing and crickets chirping all about the sunlit lakes and woods is beautiful.
In sentences that have two or more subjects joined by and, use a plural verb:
What else you can do inside qs leap ?
E.g. The actor and director are talking in the dressing room
But in sentences that have two singular subjects joined by “or”, “nor”, “either”, use singular verbs:
E.g. Mary or Jill is in the play
Use a singular verb for the following subjects: nothing, everyone, anything, someone, many a, neither, either, none, each, another and others that begin with any, every, some, no
Collective nouns that denote a collection of individuals usually take a singular verb. If the collection is thought of as a whole, the verb is singular. If the sentence makes it clear that the members of the collective are thought of as acting separately, the verb is plural.
In sentences that use the phrase “number of”, “the number” is singular but may be followed by a prepositional phrase with plurals. As long as “the number” is the subject, use the singular:
E.g. The number of mosquitoes in this room is driving me crazy.
Do not confuse compound subjects (TWO subjects joined by and) with prepositional or parenthetical phrases introduced by words such as “as well as”. “along with”, “not to mention”. A singular subject followed by a phrase of this sort still takes a singular verb:
E.g. The manager, as well as his assistant, is attending the meeting
The test can include agreement errors in sentences in which the verb precedes the subject, often by using an opening of “There is” or “There are”:
E.g. There is in London and New York newspapers, a self-satisfaction not found in the papers of small cities.
REMEMBER: (i) Agreement only applies when the verb is in the present tense. In the past tense, there is no overt agreement between the subject and the verb. (ii) Agreement applies only to third-person subjects. There is no distinction between a first-person singular subject and a first-person plural subject.