GMAT Sentence Correction (SC) | Re: By 1999, astronomers had discovered

A:had discovered 17 nearby stars thatare orbited by planets
stars are still orbited by planets. hence present tense is correct. we use present tense for universal truths.

B: had discovered 17 nearby starswith planets orbiting them that were
"stars with planets" is wrong.
C: had discovered that therewere 17 nearby stars thatwere orbited by planets
there were
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