Galileo did not invent the telescope, but on hearing, in 1609, that such an optical instrument had been made, he quickly built his own device from an organ pipe and spectacle lenses.

A. Galileo did not invent the telescope, but on hearing, in 1609, that such an optical instrument had been made, he
B. Galileo had not invented the telescope, but when he heard, in 1609, of such an optical instrument having been made,
C. Galileo, even though he had not invented the telescope, on hearing, in 1609, that such an optical instrument had been made, he
D. Even though Galileo did not invent the telescope, on hearing, in 1609, that such an optical instrument had been made,
E. Even though Galileo did not invent the telescope, but when he heard, 1609, of such an optical instrument being made, he

Step 1: Understand the meaning of the sentence
This sentence presents a contrast
1: Galileo did not invent the telescope
2: But when he heard that someone had made such an optical instrument, he quickly built his version of telescope

Step 2: Perform Error Analysis on the original sentence

1: Galileo did not invent the telescope,
2: but
3: on hearing, in 1609, that such an optical instrument had been made,
2: he quickly built his own device from an organ pipe and spectacle lenses.

There are 3 clauses in this sentence as shown. Clause 2 is separated from clause 1 using ", but". All SV pairs are accounted for.
Next we will check for verb tenses.
This sentence is established in past time frame.
Clause 1 event = did not invent
Clause 2 event = had been made
Clause 3 event = built

Per the intended meaning, the events in clauses 2 and 3 are related. Clause 3 event takes place after the clause 2 event. This sequencing is shown well with the use of past perfect tense for the clause 2 event (prior event). Thus, there are no verb errors as well.

There are no other apparent grammatical errors in this sentence. The use of expression "on hearing" may sound awkward but it is not an error. If we can eliminate the remaining 4 choices based on concrete grammatical or meaning grounds, then Choice A is the correct answer.

Step 3: Perform POE

B. Galileo had not invented the telescope, but when he heard, in 1609, of such an optical instrument having been made,
Errors:
1: "had not invented" is used in isolation with no other related event in simple past tense.
2: "having been made" is unnecessarily passive.
3: No subject for verb - built.

C. Galileo, even though he had not invented the telescope, on hearing, in 1609, that such an optical instrument had been made, he
Errors:
1: No verb for subject - Galileo
2: "had not invented" is used in isolation with no other related event in simple past tense.
3: Use of "even though" changes the intended meaning. It no longer establishes a mere contrast. It now expresses a paradox which is not the intention of the author

D. Even though Galileo did not invent the telescope, on hearing, in 1609, that such an optical instrument had been made,
Errors:
1: No subject for verb - built.
2: Use of "even though" changes the intended meaning. It no longer establishes a mere contrast. It now expresses a paradox which is not the intention of the author

E. Even though Galileo did not invent the telescope, but when he heard, 1609, of such an optical instrument being made, he
Errors:
1: Redundant use - even though - but
2: Incorrect verb tense - being made - appears as a continuous action in the past. Does not communicate the intended meaning that the optical instrument was made.
3: Use of "even though" changes the intended meaning. It no longer establishes a mere contrast. It now expresses a paradox which is not the intention of the author.

I hope the above explanation helps.

Regards,

Payal

Hi gmatmadeasy,

I realized that there was a typo in my post - For choices B and D, I meant to say "no subject for verb - built" but by mistake I said "no subject for verb - made". I have edited that in my post.

Please review Choice D with the edit and let me know if you have any concerns with that.

As far as placement of "even though" in Choice D goes, your reasoning is correct. Choices C, D, and E change the meaning of the sentence since they use "even though". Even though is used when we need to express a contradictory information or a paradox. In this case we need to show a contrast (this is done well using 'but').

For the sake of completeness, I will edit my post to include the meaning error as well in Choices C, D, and E.