The Question

      Dans la conception de matériel pédagogique, il est préférable de:
      1. découper la difficulté en un séquence d'étapes de progressivitlé très fine, de telle sorte que chaque étape
          représente une difficulté minimale par rapport à la précédente.
      2. concevoir des étapes de difficulté moyenne mais en donnant de l'aide à l'élève di nécessaire.
      3. concevoir une situation assez difficile, dans laquelle le sujet affronte la tâche dans toute sa complexité et le laisser
          se débrouiller petit à petit.

The Theory behind the question

      A principal theory behind the question is a pedagogic one: mastery learning which suggests that the focus of instruction should be the time required for different students to learn the same material. So the challenge of instruction becomes providing enough time and employing instructional strategies so that all students can achieve the same level of learning. The basic principle here is to improve the efficiency of teaching. Teaching procedure is supposed to be gradual, i.e. step by step. If the student failed in the first step, it would be useless to go to the second one. In another word, the first step is pre required for the second one. If the student tends to do something that is beyond his ability, he is simply wasting his time. Thus it is better to test if he has acquired the pre required knowledge or skill before each step.
      The second choice bears the idea of exploiting errors. According to cognitive sciences, we comprehend the world as a whole of mental representations. Although some of the representations are coherent to our perceptions they are incompatible to the theoretical models. Sometimes our perceptions may be quite different from the theoretical models. Didactic works show that although the perceptions we had are incorrect, they often survive the theories we learn later. It often happens that after several months of studying, students may still ask questions that show the representations. So at the beginning of learning it is necessary to diagnose these wrong representations and thus to "attack" them, i.e. to propose activities which allow the students to realize the limits of his representations.

Personal Opinions

       This question is a very good one in that it is encountered in no matter what kind of teaching, both traditional and CAI. It is pre required to compose teaching materials before a real instruction begins.
       The choices are very well composed except that the age group is not specified, which is very important in selecting a choice. For little pupils, the most possible choice is the first one since if they realize they are making progress they will be encouraged and eager to learn. For younger pupils encouragement is more important. For older ones I think the most probable choice is the second one since they are more independent and more able to deal with difficulties. If the rhythm of the material is too slow they would lose interest in it. If they can obtain help when they encounter difficulties and finally succeed in tackling the problems they will have a feeling of success and a sense of making progress, and then be encouraged to deal with other problems even though the material is  difficult. But if the material is extremely difficult and complicated and without any help, and the pupil is left alone to deal with it, I don't think he would succeed in learning it, even though he can succeed in some he will feel frustrated and hopeless in the end.
      On the other hand, the pedagogic material for traditional instruction is quite different from that for CAI. The traditional material is designed for a specific group of students and there is only one level of difficulty. The students have no choice but to follow the teacher. So in composing the material, the difficulty level and steps should be an important element. But in CAI the students do have choices. Generally speaking, a pedagogic software is designed for students of different levels. A student can choose a difficulty level according to his own situation. So in designing a pedagogic software, there is no problem in deciding the difficulty level, since it can be designed with several. What is important here is to set up the rhythm of difficulty and give as much help as possible. The student is probably working alone most of the time. He should get help whenever he meet difficulties and  learn step by step. Thus he will not lose hope or feel frustrated and keep on learning.