What is the conclusion reached by the author after studying sustainable development?

The author has only just begun to learn about sustainable development.
The author has learned about the different joint efforts of the world to protect the environment.
The author has learned about the different parts that make up our planet, such as the different parts of our ecosystems, the cycles of different elements, or the importance of diversity.
The author hopes that people will become aware of the damage we have caused to our planet over the last centuries and that we can stop and reverse it.
a) Only I and II are correct.
b) Only II and III are correct.
c) Only III and IV are correct.
d) Only II, III, and IV are correct.