1) Galileo did not invent the telescope, but on hearing, in 1609, that such an optical instrument had been made, he
2)Galileo had not invented the telescope, but when he heard, in 1609, of such an optical instrument having been made,
3)Galileo, even though he had not invented the telescope, on hearing, in 1609, that such an optical instrument had been made, he
4)Even though Galileo did not invent the telescope, on hearing, in 1609, that such an optical instrument has been made, he
5)Even though Galileo did not invent the telescope, but when he heard, in 1609, of such an optical instrument having been made, he
My Answer: 4 is a wrong choice.
Reasoning: I thought the original sentence is incorrect because "But on hearing" appeared as an incorrect idiom. Hence my choice is any sentence with even though.
Option 3 has an incorrect modifier after first comma.
Option Even though and but when are redundant.
However my choice was wrong. At this time after months of preparation I am still unable to figure out correct choice in sentence correction. Not only that, I am still unable to understand the reasoning behind correct answer choice [spoiler](1)[/spoiler]
