prepositional phrases - singular or plural

The Quick Answer
When a term like a box of nails is the subject of a verb, the first word (i.e., a box) is the one that determines whether the verb is singular or plural. The prepositional phrase of nails has no effect on the verb at all.

Find the Subject

When a term like a box of nails is the subject of a verb, the first word (i.e., a box) determines whether the verb is singular or plural. The words that follow (in this case, of nails) do not affect the verb at all, even though they are usually physically closer to it. (These words are known as a prepositional phrase because they start with a preposition (in this case, of).



More examples:
  • The evacuation of the offices is the floor manager's responsibility.
  • (evacuation is singular, hence is and not are)
  • A box of tapes were discovered in his car.
  • (The word box is singular. It should be was and not were.)
  • A combination of factors were the cause of the crash. †
  • (combination is singular)
  • He [Bernard Shaw] hasn't an enemy in the world, and none of his friends like him. (Oscar Wilde)
    (Marking this wrong is a little harsh, but you should try to treat the word none as singular (if for no other reason than many of your grammar-savvy readers will want it to be singular). Therefore, none of his friends likes him is slightly more acceptable. Read the Beware section on the right.)

See Also

What are prepositions? The object of a preposition Forming plurals Forming plurals of compound nouns Forming plurals (table)