（1）     T-4-Q17

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.

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, in1609, 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 had been made,

Even though Galileo did not invent the telescope, but when he heard, 1609, of such an optical instrument being made, he

答案是A, 请问A该怎么理解,he后面是一个句子,前面不要连词吗?

句子1+but 句子2

句子2：介词+分词+插入语+that从句，主句