The correct answer is D. No improvement.
The sentence “The contractor did not keep his promise that the work will be finished before the
end of the week” is grammatically correct and conveys the intended meaning clearly. The use of the modal verb “will” is appropriate, as it expresses the contractor’s intention to complete the work by the end of the week. The use of the negative form “did not keep” indicates that the contractor did not fulfill his promise.The other options are not as effective as the original sentence. Option A, “shall,” is a formal modal verb that is typically used to express obligation or necessity. In this context, it would sound strange to say that the contractor “shall” finish the work before the end of the week. Option B, “would,” is a modal verb that is typically used to express possibility or willingness. In this context, it would sound like the contractor was not sure whether or not he would be able to finish the work by the end of the week. Option C, “could,” is a modal verb that is typically used to express ability or permission. In this context, it would sound like the contractor was not able to finish the work by the end of the week, even though he wanted to.
Overall, the original sentence is the most effective way to express the intended meaning.