Change the voice: The Engineers are repairing all the broken bridges.

All the broken bridges are being repaired by the Engineers.

All the broken bridges were repaired by the Engineers.

All the broken bridges are repaired by the Engineers.

None of these

All the broken bridges are being repaired by the Engineers.

"Are repairing" is present continuous tense → passive becomes "are being repaired".

Subject (The Engineers) becomes agent at the end: "by the Engineers".