Answer:
Step-by-step explanation:
Scarcity exists when there are 
limited
resources to meet unlimited needs and wants. Because of 
scarcity
, we must make choices about how to use resources. All the options for using resources that are not chosen are called 
trade-offs
.
Opportunity cost
is the next-best alternative for the use of resources.
Marginal means using one 
additional
unit of a resource.