I had been doing the work for five days. Change the voice

Question: I had been doing the work for five days. Change the voice--

A) I had been done the work for five days.

B) The work had been done by me for five days.

C) The work had been being done by me for five days.

D) The work had been doing by me for five days.

Answer:
C) The work had been being done by me for five days.

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