They________ their work by tomorrow.

Correct Answer B. Will have completed 

The question “They Will have completed their work by tomorrow” suggests that there is a group of people (referred to as “they”) who have a task or project that needs to be finished. The missing word in the question is asking for the appropriate verb tense to indicate when the completion of the work will occur.

The correct answer, as mentioned earlier, is “B. Will have completed.” This option is in the future perfect tense, indicating that the action of completing the work will occur before a specific point in the future, which is tomorrow in this case.

Using “will have completed” implies that the work is currently in progress or still needs to be done, but it will be finished by the time tomorrow arrives. It suggests that the individuals will continue working and ensure that the task is completed within the given timeframe.