if you have just ONE OF THE + PLURAL NOUN +
WHO/THAT + ______, and it's NOT "the only one",
THEN "____" MUST be a PLURAL VERB.zero exceptions.
example:
that's one of the birds that fly over my house at night.
here's the rationale, if you care about reasons: the idea is that there is a whole group of NOUNs (whatever they are) that do ______, and we're singling out one of them.
notice that the RED-COLORED RELATIVE PRONOUN (WHO/THAT) is absolutely crucial here.
if that isn't there - i.e., if "one of the NOUNs" is actually the SUBJECT of the ____ verb - then you take a singular verb instead.
example:
one of the birds flies over the house; the other one flies past it.
--
finally, to complicate things further,
THE ONLY ONE OF THE + PLURAL NOUN + WHO/THAT + ______ requires a SINGULAR verb for the "_____".
in this case, only one of the NOUNs actually does whatever "_____" refers to, so we stick with the singular verb.
example:
Marina is the only one of the girls who
has ever been to India.
the following examples are both correct:
(1) he is
one of the people who
bake special cakes.
(2) he is
the only one of the people who
bakes special cakes.
this actually isn't as hard as pure memorization might make it seem: all you have to do is think about the LITERAL MEANING of what you're writing.
in my #1, there are lots of people who bake special cakes, so "bake" should be plural.
in my #2, the man in question is the ONLY person who bakes special cakes, so the verb should be singular.
--
here's another way to think about it: you can DECONSTRUCT the sentence, and tell exactly which noun / construction the verb "belongs" to. (i have no idea whether this is a formal grammar concept or not, but it works.)
in my #1:
PEOPLE bake cakes. (--> plural "bake")
he is one of them.
(he is not "one who bakes cakes")
in my #2:
there are a bunch of PEOPLE.
he is THE ONE who BAKES cakes. (--> singular "bakes")
(there are not "people who bake cakes")
CAVEAT:
this is one of those things that are RIDICULOUSLY hard to memorize, but is actually pretty easy just to
deduce from context. so, unless you're prepared to memorize a whole lot of easily confused, easily forgotten rules that are extremely subtle, you should just think about the context and go from there.
* for instance, given
X is
only one of the factors, albeit an important one, that (keep/keeps) the market from spinning out of control
it's clear that there are MANY factors, ALL of which keep the market from doing blah blah blah, and that X is just one of them.
since there are MANY factors keeping...., we should use the plural "keep".
* on the other hand, given
X is
the only one of the factors that (keep/keeps) the market from spinning out of control
it's clear that there are many factors, but NONE OF THEM EXCEPT X keeps the market from doing blah blah blah.
since X is the ONLY factor keeping...., we should use the singular "keeps".
In 99.9% of these, you'll be able to just think about the context in this way, saving yourself a horrendous amount of time and effort.
(The above answer has been taken from Ron's answer on BTG.)
_________________
When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. - Henry Ford
The Moment You Think About Giving Up, Think Of The Reason Why You Held On So Long