Which one of the following is the most effective correction technique in language learning?

Before entering the classroom, a teacher asks himself, 'What changes in the behaviour of the students can I bring about through this lesson?' Such intended changes constitute the teacher's:

A class V teacher gave students a task to write a story. While students are writing, the teacher walks around the class helping those who make errors or ask for new words. Here, the teacher is playing the role of a: