This question has come up three times in as many days, so I've made it a FAQ.
Here's what you need to know:
Here is the pattern you need to become familiar with:
one of the NOUN + that/who +PLURAL VERB
The reasoning is as follows: we are saying that this person (or thing, or whatever) is a member of a group. What group? Te group of people (or things) that do or are whatever.
- She is one of the few people who know how to speak Esperanto.
- This is one of the cars that run on hydrogen.
So far, every single time I've seen this on GMAT SC, it's been set off by "one of..." So keep an eye out for "one of"!!
And this one's tricky because we become sort of trained to ignore the stuff inside of prepositional phrases, but as we've just seen, it's important to remember that a modifier can modify any noun, no matter where it is.