Answer:
I think it's C
Step-by-step explanation:
Economic choice... It WOULD be that if you were talking about money.
Opportunity Cost... the loss of potential gain from other alternatives when one alternative is chosen. So it can not be that.
Scarcity... This one means that there is too little of something. So I used context clues to find that out.
Specialization... Oh, who cares anymore I answered the question!
Hope I helped! ☺