Correct the below mention sentence in the bracket. (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, in 1609, of such an optical instrument being made, he

a. Galileo did not invent the telescope, but on hearing, in 1609, that such an optical instrument had been made, he

Explanation:

Looking at the given sentences, the first thing we need to ascertain is the tense form. The use of "did not" makes it a past tense which is also supported by the use of the past perfect tense "had been". Moreover, the conjunction "but" perfectly compares/ presents a contrast between two ideas or opinions. Thus, option A is correct.

The other options such as B, C, D, and E are all incorrect.

Option B is wrong as it uses "had not invented" which should be in the simple past tense form. Moreover, it did not specify the pronoun "he" for the device built in the latter part of the sentence.

Option C is wrong as it follows the same verb tense form error as in option B.

Option D is wrong with the absence of the pronoun "he" as in option B. Also, the use of "even though" presents faulty sentence structuring.

Option E is wrong as in option D and also the redundant use of the "but" after the use of another comparing word "even though".

a). Galileo did not invent the telescope, but on hearing, in 1609, that such an optical instrument had been made, he

Explanation:

The first sentence i.e. option a rectifies the given sentence correctly. It correctly employs past perfect tense where the first action(telescope had been made) is written in 'had + V3' and the latter action(built his own version) in 'V2.' The use of 'but' helps in displaying the contrast effectively.

The second option is incorrect as the general facts are stated in the past indefinite and it also contains punctuation error, misses the subject 'he' for the verb 'built.' The third option also contains the verb error of inappropriate use of past perfect and the error in the use of the pronoun 'he' succeeding 'even though' as the subject is given at the start of the sentence. The options d and e are wrong due to the inappropriate use of 'even though.' Thus, option a is the correct answer.

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