1.What must Rob do?
He must go through security control.
2.What mustn't Rob do?
He mustn't take a bottle of water.
3.What mustn't Mark and Betsey do?
They mustn't cross the line.
4.What needn't Rob do?
He needn't show them his passport.
5.What needn't Mark do?
He needn't say "goodbye".
Удачи!... ;)