Übungen zur Kommasetzung

Welcher Satz ist jeweils korrekt?

1. Could you help me please?
   Could you help me, please?
2. Please don't smoke here.
   Please, don't smoke here.
3. An orange juice and a hamburger please.
   An orange juice and a hamburger, please.
4. What's the time please?
   What's the time, please?
5. Please be home by eight o'clock.
   Please, be home by eight o'clock.