Question

the students will have completed the work before Sunday (begin the work) ​

Answer 1

Explanation:

Work will have to be completed by the students before Sunday.

Answer 2

Answer:

The work will have been completed before Sunday. (if you want to omit the agent)

The work will have been completed by the students before Sunday. (if you don't want to omit the agent)

Explanation:

All I basically did was change the sentence from active to passive voice.

hope it helps