What is the purpose of the text?

To discuss the importance of good teaching and the characteristics of effective teachers.
To present research on the impact of teacher effectiveness on student achievement.
To provide examples of effective teaching practices.
To analyze the differences between novice and experienced teachers.
a) Only afirmations I and III are correct.
b) Only afirmations II and IV are correct.
c) Afirmations I, II and III are correct.
d) All afirmations are correct.