The question is about the nature of instructional communication in the distance education mode. Let's analyze each option to understand why the correct answer is structured and interactive.

1. Unstructured: In the context of distance education, instructional communication is not typically unstructured. Distance education usually involves organized curricula and defined learning paths, making this option less likely.
2. Self-regulatory: While self-regulation is a component of distance learning, as students must manage their own study schedules, the instructional communication itself is not inherently self-regulatory. It is more guided to ensure understanding and progress.
3. Informal: Instructional communication in distance education is not typically informal, as it needs to follow a formal educational structure to achieve specific learning outcomes. Thus, this option is not suitable.
4. Structured and interactive: This is the correct answer. Distance education relies on structured course materials and interactive elements, such as online discussions and collaborative projects, to facilitate learning. Instructors often use learning management systems to deliver content, track progress, and engage students through various interactive methods.

In conclusion, instructional communication in distance education is structured and interactive as it involves organized delivery with opportunities for student-teacher and student-student interactions to enhance the learning experience.