GMAT - Sentence Correction

[CharlesL815]

[question text removed]
OA - B

Hi everyone ,
It is my first post on this forum, but all of you guys have helped me a lot to progress in my GMAT journey - that I hope will end soon - especially you Ron. Thank you for your SCIENCE and pedagogy.

I have paid for an access on the 2019 GMAT official guide Online, where I came across this SC for which I did not understand the explanation.
Rhetorical Construction; Logical Predication
The statement provides a definition of the term quicksand as sand that has been saturated with water to a certain degree. Many of the flaws in the incorrect options have to do with how this degree of saturation is described.
Correct. In this option, the clause introduced with that contains a proper statement—with both a subject and verb—which implies a degree of saturation with water. This option thus has none of the flaws discussed in connection with option A.

I was hesitating between A and B and finally picked A for the idiom So + adjective+ infinitive that I have learned on this forum.
So please, could someone can give me an explanation that hold for the use of this idiom or it depends on the meaning of the entire sentence?

Thank you very much for the help. ( Non native - sorry if any langage mistake)

[Sage Pearce-Higgins]

Thanks for your post. Please check out the forum guidelines: unfortunately we can't discuss problems from paid-for resources such as the OG 2019 as we don't have copyright to reproduce the problems on this public forum. Sorry.

You should also realize that the explanations in the Official Guide are often rubbish - they can be vague, subjective, or even contradictory. For that reason we've written explanations to OG problems in our Navigator app. That said, it looks like it hasn't been upgraded for the new 2019 guide yet. For that reason, I'd recommend buying a 2018 guide if you plan to use Manhattan Prep resources.

As for the idiom, we say 'so [adjective] that ...', for example, 'I was so tired that I fell asleep on the train', or 'The company was so large that it was impossible to manage.' Take a note of that idiom.