Answer: A) Scaffolding
Explanation: Scaffolding can be simply refered to as an instructional method of teaching where teachers or tutors guide their students in a step by step manner to solve a problem, the influence or involement of the tutor in the problem solving decreases or fades as the student becomes more and more competent in problem solving. This allows for the student to work independently except if the student request for the intervention of the tutor.
Alberto's teacher has used the constructive principle of scaffolding in teaching him.