Mostly subject verb agreement issues: One of the

This point is rather confusing ...however, from my experience, i notice that "that" does modify the noun preceding all prepositions of the noun phrase ....for your example, "that" should modify "X"

p.s: hik, i'm not a master or a guru or so forth . I still have to learn a lot from all of you! Let's share and help

Example:

One of the substances that tell individual genes...
CORRECT (that modifies substances, thus plural, hence 'tell')

One of the substances that tells individual genes...
INCORRECT

Yes, you're correct

I now recall this point is a favorable trap in GMAT

I still cannot not uderstand this concept
Can you please explain this one ..which one is correct and why?
provides or provide?
One of the substances that provides/provide the strongest amount of energy to generate life is manure.

Uhm, it's quite confusing
Back to the example " one of the children that are/is playing "

The addition of "the children" here is to clarify the kind/type/group to which "one" belong ----> what's the special point of this kind/type/ group is further indicated by "that" clause ----> logically, "that ...." modifies " the children" -----> the verb of "That" clause must be of "the children", that is to say, it must be plural.

I think this reasoning can be applied generally.

One of the substances that provides/provide the strongest amount of energy to generate life is manure.

The correct form of this sentence should be
One of the substances that provides the strongest amount of energy to generate life is manure.

Lax ..I think I need more explanations please..

IMO, it depends on the context a lot ....
let's imagine ... the both speakers had talked about "the substances" before this sentence was made ....in this case, "one of the substances" is to indicate that there's solely one among the kind ......what's so special about this one? ...it's further indicated by "that" clause ...thus, that clause serves "one" instead of " the substances" ---> the verb must be singular

In case, there's no such context ...."That" clause logically serves "the substances " ---> verb must be plural ...

In GMAT, i don't think we're provided by outside/ pre- context ...so the second case is more applausible ....

I recall myself encoutered a SC of this kind ...lemme find it and post here soon,okie?!

one of a greater number. When constructions headed by one appear as the subject of a sentence or relative clause, there may be a question as to whether the verb should be singular or plural. The sentence One of every ten rotors was found defective is perfectly grammatical, but sometimes people use plural verbs in such situations, as in One of every ten rotors have defects. In an earlier survey, 92 percent of the Usage Panel preferred the singular verb in such sentences.

Chk this out https://www.bartleby.com/64/C001/043.html-
According to this both are right but the first usage is more widely accepted.