Agreement After Expressions of Quantity

The subject (all, most, or some) can be singular or plural, depending on what follows the preposition of.
If the subject (all, most or some) refers to the singular noun, then the verb must be singular
If the subject (all, most or some) refers to the plural noun, then the verb must be plural

Ex. :
Most of the meal was delicious (singular)
Most of the meals were delicious (plural)
Most of the food was delicious (uncountable)

(all, most, some, half, part)-of the (object)-verb
When an expression of quantity using of is the subject, the verb agrees with the object

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