Hi anksm22,

This SC is based heavily on Modification rules (all those commas and intervening phrases provide the clue). We're given information about how Galileo did not invent the telescope but he built his own version after hearing about the telescope.

1) Pronouns: The modifying phrases give us information about Galileo and the telescope; the end of the sentence tells us what Galileo ended up doing. We need a specific reference to Galileo to complete the last part of the sentence - the pronoun "he" is required. Eliminate B and D.

2) Redundancy: Correct GMAT SCs won't state an idea twice (re: use two words that mean the same thing). Answer E uses "even though" AND "but" to convey a contrast. The sentence does NOT need them both. Eliminate E.

3) Efficiency: If all other rules are correct (and the intent/meaning of the sentence is not changed), the correct answer tends to be the shorter (and more efficiently worded) option. Answer A tells us "Galileo did not invent the telescope, but...."; Answer C tells us "Galileo, even though he did not invent the telescope..." Answer A is far more efficient. Eliminate C.

Final Answer: A

GMAT assassins aren't born, they're made,
Rich