GMAT Sentence Correction (SC) | Re: Until a few centuries ago, any large bones discovered in the

egmat ,sayantanc2k ,

Can anyone explain the correct usages of words such asknown, assume, and named .
Every time these words appear in the options with different usages, I took a lot of time to figure out which way is correct. Some of the variations appeared in GMAT-Prep are:

known as, known to be
named as, to be named
assumed as, assumed to be

Please explain.

Thank You.
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