Eric Townsend wants to be a teacher[color=red], nurse[color=red], or social worker.
Investigate workers often do market surveys[color=red], develop military strategies[color=red], or tackle economic problems.
Adela Sanchez is energetic[color=red], self-confident[color=red], and ambitious.
Sanchez hopes to get a leadership job in sales[color=red], politics[color=red], or business.
I got them all correctly?
#7-- The second comma is optional; it is used mostly in British English.
#8-- Investigative. The second comma as with #7.
#9-- The second comma as with #7.
#10-- The second comma as with #7.
Hey, I’ve seen your post guys. I’ll be working on this - specially on that wiki.
Aikuzo, don’t spend too much time on this: it is not important. Just choose whichever way you like best.
It’s just that after you’ve made your choice for or against the comma, you might get killed by either Cantabrigians or Oxonians, respectively; that’s all.
As mentioned, the serial comma is your choice to make. Personally, I like it because it ensures clarity in more complex series sentences. Plus, it’s a nice homage to classic punctuation.
Same here!
Waaaa!
I cancelled the party I was to attend to just to study this and now… I’m just kidding! 
Thank you all guys, I’ll follow you guys and Bolandnm suggest and move to the next part.