In Economics, What Is the Definition of Natural Resources

Multiple Choice

In economics, what is the definition of natural resources?  

A)  the buildings, equipment, and human skills used to produce goods and services 
B)  the time and the physical and mental efforts used to produce goods and services 
C)  the imagination required to develop a new product or process 
D)  all gifts of nature used to produce goods and services NOT considered scarce because they are NOT produced by society