You received $50 as a birthday gift chose to spend it on new wallpaper for your room. the opportunity cost of this decision is:

The opportunity cost of reaching $50 for your birthday and spending it on new wallpaper for your room is: not having money anymore but having wallpaper. Opportunity cost is defined as what you are giving up to gain something else. In opportunity cost, you are always making a decision out of possible alternatives. 

1.world in spatial terms2.places and regions 3.human systems4.physical systems5.geography and it's uses6.environment and society

Ais the correct answer