GMAT Sentence Correction (SC) | Re: Many of them chiseled from solid rock centuries ago, the

Levels are not that scrutinized most of the times and are added by the poster of the question based on what he or she thinks.

Here are my thoughts about the question though

The main difference between the sentences does not lie in the words you marked in bold, but in their locations.

In the 1st sentence,
...

---