Mixed with an equal part of water, ethylene glycol

can someone please explain why not "so low as" and why "as low as"?

Ron in manhantan forum said that
as many/much/few/little+noun+ as
is idiom
we need many,much, few .little to have noun between as...and as.
so, choice C is wrong

Hi arorni, this is just an idiomatic construct: as low as, as high has, as good as, as small as etc.

You just need to be comfortable with this handy idiomatic pattern.

Hi, arorni
as ... as : used to compare two items either in a positive or a negative statement. --> (as low as) or (not as low as) both correct
so ... as : used to compare two items in negative statement only. --> (not so low as) is correct , while (so low as) is incorrect.

Mixed with an equal part of water, ethylene glycol, a compound commonly used as an automotive antifreeze, is effective at temperatures as low as –30 degrees Fahrenheit.
A. temperatures as low (whenever we use as x as y it means x and y are equal in some context . here x and y are low in category of temperatures . so this is correct usage)
B. temperatures so low (the idiom we have is of as X as Y another idiom not so much X as Y both have different usage .) reject
C. as low temperatures - here we don't have the category in which X and Y would fall . after AT we need a category (preferably noun form ). reject
D. as few (low vs few - few is used for countable noun but here we want to show that degree was LOW (correct usage for comparison ) Reject .
E. as little (little - uncountable ) degrees are countable - reject

Mixed with an equal part of water, ethylene glycol, a compound commonly used as an automotive antifreeze, is effective at temperatures as low as ???30 degrees Fahrenheit.
A. temperatures as low
B. temperatures so low
C. as low temperatures
D. as few
E. as little

Kindly tell the rational why B and C is wrong

Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.