Yes. I do not know how to realize awkward sentence.

the best way is to remember specific cases.

for example, "of noun of noun" is awkward because "of" is used 2 times. I do not remember other cases

However,gmat want to have a grammatical sentence before a beautiful sentence. So,we check for grammar error before check for meaning logic and style. That means gmat accept an award sentence not a ungrammatical sentence if there are only these sentences left. gmat will accept beautiful sentence not award sentence if these sentences exist.

ok, remember specific cases and check grammar first.

thanks! i will start memorizing them.