求翻译：．教师的角色随着教学环节的变化而变化。在介绍新材料，或提出供小组讨论或调查的问题或任务时，教师充当的是组织者和引导者的角色。小组开展合作与交流的时候，教师的角色又变为一个促进者和合作者。有时又根据学习任务的难度和学生的实际情况充当指导者。是什么意思？

. The role of teachers with the teaching of the change. Introducing the new material, or presented for group discussion or investigation of the problem or task, the teacher acts as the organizer and guiding role. Group cooperation and exchanges when the teacher's role becomes a facilitator and colla

. the role of teachers with teaching the change for the sake of change. In introducing new material, or for the panel discussion or investigation of the question or task, teachers act as the organizers and guiding role. Group cooperation and exchanges, the role of teachers also turned into a facilit