The meaning of all of those choices are relatively same, however the difference arises in the probability of the certain action happening.
"The train will leave"...this implies that the situation is probable, and that the train leaves at the specified time every day.
"The train is going to leave"...this implies that there preparations currently underway and if complete, the train will leave at that particular time.
"The train leaves"...this implies that the train departs at the specified time every time.
"The train is leaving"...this implies that all necessary preparations have been made and the train will leave at the specified time.
I don’t think anyone can help you on this unless you post whatever the play is
The Stage Of The Conflict.
Here are the answers for the exercise
1. have been
2. did she meet
3. has he been
4. went
5. have we owned
6. did she graduate
7. did the children go
8. didn't write
9. drank
10. Has she ever tried
11. have you lived
12. Have you ever been
13. didn't go
14. did you go
15. Have you eaten/ Did you eat (Both is correct)
16. have wanted
17. has had
18. didn't see
19. did you have
20. Has he ever played
can you show me the sentences so i can help you