Hi all.
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.
Since it is not difficult to understand the meaning of this sentence, let’s quickly get into the
error analysis:1. Use of past perfect tense is correct because 1609, the telescope had been already made and after that Galileo made his own version of the instrument. So there are two past events and “had been” correctly denotes that telescope was first made and then Galileo came up with his own version.
2. “but” correctly presents the contrast.
3.
No errors.PoE:a) Galileo did not invent the telescope, but on hearing, in 1609, that such an optical instrument had been made, he:
Correct for reasons stated above.
b) Galileo had not invented the telescope, but when he heard, in 1609, of such an optical instrument having been made,
Incorrect.1. Use of “had not invented” is incorrect because the sentence here just presents a general fact that should be written in simple past tense.
2. Use of “having been made” is also incorrect in this choice.
3. This choice also misses the subject “he” for the 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:
Incorrect.1. Same verb tense error as in Choice B.
2. Use of pronoun “he” after “even though” is incorrect because Galileo has already been mentioned in the beginning of the sentence. This construction makes Galileo hanging without a verb.
3. Use of “even though” is incorrect. This expression is used to present contrast in that it denotes two opposite situations. For example:
Even though he is poor, he has managed to go to a good B school.
However, this choice does not present opposite situations. It simply says that Galileo did not invent telescope but he later developed one. There is co opposite things going on in here.
d) Even though Galileo did not invent the telescope, on hearing, in 1609, that such an optical instrument had been made,:
Incorrect.1. Use of “even though” is incorrect as in Choice C.
2. Absence of “he” before “built” leaves this verb without any subject.
e) Even though Galileo did not invent the telescope, but when he heard, in 1609, of such an optical instrument being made, he:
Incorrect. 1. Use of “even though” is incorrect.
2. Use of “but” is redundant because “even though” already presents the contrast.
Hope this helps.

Thanks.
Shraddha
- why is "having been made" wrong. Please share the reason. Is it because "Having been made" is used for sequencing?