What is the MAIN reason the author includes the section "Challenges To Sustainability"?
(A)
(B)
(C)
(D)
It predicts some of the consequences for nations if they implement sustainable
development.
It compares two nations' experience with sustainable development and
contrasts their response to the challenges they faced.
It identifies issues that have made adopting sustainable development difficult.
It describes how sustainable development can make life harder for some
people.