which phrase best defines scarcity?

a. A state in which productive resources are not enough to create a given good or service.
b. A state in which human wants are greater than the resources available to fill those wants.
c. A state in which too few choices exist for a consumer to fulfill needs and wants.
d. A state in which the opportunity costs of a given choice are less than the benefits of a given choice.

a. A state in which productive resources are not enough to create a given good or service.