classes:  lecturer. reduce tangible theories that are difficult to understand, strengthen the exercise as well as examples but the lecturer must correct the student to know the problem.  curriculum. reduce tangible theories that are difficult to understand, strengthen the exercise as well as examples but the lecturer must correct the student to know the problem.  facility. reduce tangible theories that are difficult to understand, strengthen the exercise as well as examples but the lecturer must correct the student to know the problem.  general. reduce tangible theories that are difficult to understand, strengthen the exercise as well as examples but the lecturer must correct the student to know the problem.