The correct answer is: D. the death knell for the city.
The sentence is grammatically correct, but the word “practically” is unnecessary and should be removed. The sentence would be more concise and effective without it.
The word “practically” means “in effect” or “virtually.” In this sentence, it is redundant, as the word “ring” already implies that the eleven new flyovers would have a significant negative impact on the city.
Removing the word “practically” would make the sentence more direct and to the point. It would also be more consistent with the tone of the rest of the sentence, which is serious and urgent.
Here is the sentence with the word “practically” removed:
Activists opposing the rail project said that the eleven new flyovers to be built would ring the death knell for the city.
This sentence is more concise and effective than the original sentence. It is also more consistent with the tone of the rest of the sentence.