Which statement best characterizes an economic impact of smartphone development?
a. The production of smartphones is inexpensive and does not have a far-reaching economic impact.
b. Smartphone development is eliminating mining jobs in many parts of the world.
c. The mining of rare-earth elements is currently centered in the U.S., giving the country an economic advantage in the global marketplace.
d. The mining of rare-earth elements is currently centered in China, which poses an economic risk to other countries.