The active form of the given sentence "We were made to work by them" is: They made us work.

Here's why:

• "They made work done by us" is grammatically incorrect.
• "We worked for them" implies that we chose to work for them, while the original sentence suggests that we were forced to work.
• "They are making us work" is in the present continuous tense, whereas the original sentence is in the past tense.
• "They made us work" directly converts the passive voice of the original sentence ("We were made to work") into the active voice. It clearly identifies the subject (they) who performed the action (made) and the object (us) who received the action (work).