SC - "One of" as a subject

[User9876]

For ex - "Scientists have found one of the substances that tells genes when to activate......."

Should this be "tell" or "tells"?

[vscid]

tell.

[pk]

It would have been "tells" without the "that" so whenever u ve that, which and so fourth before the verb u should be extra careful

[HELP!]

It would have been "tells" without the "that" so whenever u ve that, which and so fourth before the verb u should be extra careful

Really? I thought it should be "tells" isn't "one" singular?
our dear MGMAT experts, please help!!!!

[Guest]

It would have been "tells" without the "that" so whenever u ve that, which and so fourth before the verb u should be extra careful

Really? I thought it should be "tells" isn't "one" singular?
our dear MGMAT experts, please help!!!!

can someone clarify this?? how the usage of that determines singular/plural sub-verb agreement??
thanks!

[Guest]

It would have been "tells" without the "that" so whenever u ve that, which and so fourth before the verb u should be extra careful

Really? I thought it should be "tells" isn't "one" singular?
our dear MGMAT experts, please help!!!!

can someone clarify this?? how the usage of that determines singular/plural sub-verb agreement??
thanks!

anyone?

[H]

I believe that "one of X" as a subject requires a singular verb form.
However, "...one of X that" can be followed by a singular or plural verb form. The choice is based on the meaning of the sentence.

[esledge]

tell/tells is a verb within a relative clause. The number of such a verb should match the number of the modified noun. Here, I think the answer to "What tells genes when to activate?" is "substances," not "one." Thus, go with the plural verb "tell."

Scientists have found one of the substances that tell genes when to activate.

Typically, a relative clause modifies the immediately preceding noun, so placement would also indicate "substances" as the subject of "tell."

However, a relative clause can modify a noun further removed if there is another necessary modifier in the way. An example:

One of the bridges that has/have been crooked finally collapsed.
How to decide? There are both singular and plural nouns: one, bridges.

One method is to put parentheses around modifiers, then decide which each modifies:
One (of the bridges)(that has/have been crooked) finally collapsed.
*(of the bridges) modifies one, the immediately preceding noun.
*(that has/have been crooked) modifies bridges (logical--many bridges could be crooked) OR one (logical, too--it may be that only one bridge that was crooked.)

In this case, either sentence would work. Such ambiguity would likely be avoided by GMAT answer choices.
(1) One of the bridges that has been crooked finally collapsed.
(Of the many bridges, the crooked one finally collapsed.)
(2) One of the bridges that have been crooked finally collapsed.
(Of the many crooked bridges, one finally collapsed.)

(1) still seems less than ideal to me, but the important take-away is to consider the intended meaning along with the structure of the sentence.