The correct answer is: D. The entire block will be demolished by them.
The other options are incorrect because they do not accurately reflect the meaning of the sentence.
Option A, “The entire block is being demolished,” is incorrect because it does not specify who is doing the demolishing. The sentence could be interpreted to mean that the entire block is being demolished by someone other than “they.”
Option B, “The block may be demolished entirely,” is incorrect because it does not express certainty. The sentence could be interpreted to mean that there is a possibility that the entire block will not be demolished.
Option C, “The entire block will have to be demolished by them,” is incorrect because it does not express the idea that “they” are the ones who will be doing the demolishing. The sentence could be interpreted to mean that someone else will be demolishing the entire block, and “they” will have to deal with the consequences.
Option D, “The entire block will be demolished by them,” is the correct answer because it accurately reflects the meaning of the sentence. The sentence states that “they” will be the ones who will be demolishing the entire block.