Explanation
The correct option to fill in the blank is:
B) haven't
Explanation: In this sentence, the phrase "We have finished our work" indicates that the action of completing the work has been done in the past. Therefore, the correct verb form to use is "haven't," which is the contraction of "have not." This indicates that the action of not having finished the work is still true at the present moment. Option A) aren't (contraction of "are not"), Option C) didn't (past tense of "do not"), and Option D) shouldn't (contraction of "should not") do not convey the intended meaning in this context.