1. They will return in the night.
(Frame a Wh-question to get the underlined part as an answer.)
2. They went to sleep. (Write the sentence in Past Progressive tense.)
3. Why did the Greeks make such a huge horse? (Rewrite the sentence using Past Perfect tense.)
4. The walls are no longer necessary. (Add a question tag.)
5. The Greeks have gone. (Rewrite the sentence using Simple Past tense.)