Experienced wordsmiths know that, in a sentence, a singular subject requires the singular version of the verb. Or do they? Even professional writers sometimes trip on this rule. For example, here’s the lead from a news item published on the Des Moines Register website:
To Tom and Irene Frantzen, the mountain of corn cobs sitting in their hoop building are a valuable commodity.
Here, the subject is “the mountain of corn cobs,” and because only one “mountain” is mentioned, the subject is singular. Ignoring the misspelling of "corncob," the sentence should read:
To Tom and Irene Frantzen, the mountain of corn cobs sitting in their hoop building is a valuable commodity.
