Agreement After Prepositional Phrases

Subject/verb agreement is simple:
If the subject of a sentence is singular, then the verb must be singular.
If the subject of the sentence is plural, then the verb must be plural.
An -s on a verb usually indicates that a verb is singular
An -s on a noun usually indicates that the noun is plural

Ex. :
The door to the rooms are* locked
The doors to the room is* locked
*indicates an error

The correct are:
The door to the rooms is locked
The doors to the room are locked


S____________________________V
(prepositional phrase)

When a prepositional phrase comes between the subject and the verb, be sure that the verb agrees with the subject