Explanation:

The original sentence is incorrect.

Reason: 

1st. As we can observe that the sentence is made in present tense, usage of past form ‘disturbed’ is erroneous here. Instead of ‘disturbed’, ‘disturbs’ (because the subject is singular) should be used here.

2nd. ‘Conscious’ means ‘aware of and responding to one's surroundings’ and the word doesn’t make any sense in the context of the sentence. Instead of it, the noun ‘conscience’ that means ‘a person's moral sense of right and wrong, viewed as acting as a guide to one's behaviour’ should be used here.

Ex. He had a guilty conscience about his desires.

Therefore, among the given choices option D replaces the bold part most appropriately.

The sentence after replacement becomes:

Poverty is too much with us and its presence across vast stretches of our country disturbs our conscience.

Option D is hence the correct answer.