In the context of external environment, which of the following is true of natural resources?
a. Vast differences in natural resources result in minor shifts of wealth among countries.
b. Petroleum is the only natural resource that affects international marketing.
c. Steep declines in the price of oil in 2014 and 2015 had a positive impact on America's oil producers.
d. The past decade has witnessed shortage of natural resources.
Answer: d. The past decade has witnessed shortage of natural resources.