Answer:
This sentence is already in the passive voice. Its active voice is 'They burned the ship.
Hi! The sentence you gave is a complex sentence. For a sentence to be compound, it should contain multiple subjects or predicate. On the other hand, for it to be complex, a subordinate clause must be present.
We can notice that the clause "that were built under the city" is a clause that cannot stand alone thus this will tell us that the sentence is complex.
ANSWER: D. Complex
I would say a but i don't know. I am not for sure.
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