abhasjha wrote: What is wrong with option D?

Clay is not as hard as cement.
Conveyed meaning:
Clay is not as hard as cement [is hard].
The words in brackets are omitted, but their presence is implied.

D: Granitic soil is not as hard as to make burrowing difficult.
Conveyed meaning:
Granitic soil is not as hard as to make burrowing difficult [is hard].
The implied comparison makes no sense.
Eliminate D.

thank you mitch.

I thought

"So hard that" was wwong, I thought that the correct way to use 'so' was in the format "so ... as to ...". Am I wrong? When can I know which to use?

Thanks

renatofarias wrote:I thought

"So hard that" was wwong, I thought that the correct way to use 'so' was in the format "so ... as to ...". Am I wrong? When can I know which to use?

Thanks

"So x that y" is definitely a valid construction.

"So x as to y" isn't technically wrong, but GMAC seems to have a complicated stance on. (In an earlier OG, an answer choice was deemed wrong because it contained the construction. In a later version, the correct answer actually contained it. The GMAT tends not to depart from common usage, and my go-to usage guide deems "so...as" to be perfectly acceptable.)

My advice: don't use this split as a decision point. There will be other differences among the answer choices and other elements of the incorrect options that are definitively incorrect.