6. Which of the following statements is true?

a	There is concern about whether economic growth is sustainable. The earth only has a limited number of resources which are being consumed at alarming rates.
b	Those in defense of economic growth say that it has significantly reduced the standard of living of billions of people.
c	Those in defense of economic growth also say that human imagination can solve environmental and resource issues.
d	All of the above.
e	Only a) and c)