Yesterday we determined that the verb form in a dependent clause is determined by the word the clause modifies, which sets us up for a bit of a dilemma in this sentence:
...John is one of the men who IS/ARE attending the convention.
To determine whether it is is or are in "who is/are attending the convention," we have to look at what the sentence is saying.
Is John one of many men in attendance? If so, then the clause modifies men, and the verb is ARE.
Is John the only one of the many men in attendance? If so, then the clause modifies one, and the verb is IS.
The sentence is saying that there are many men attending the convention and that John is one of them. It is correct as
...John is one of the many men who ARE attending the convention
Every grammar test on the planet uses this sentence to separate the wheat from the chaff. :-)
Happy punctuating!
Margie