What makes a radio documentary distinctive?

Kindly, listen to the link and answer the questions below: http://www.bbc.co.uk/academy/production/article/art20130702112135707

1- What makes a radio documentary distinctive?
2- What does a radio documentary encourage the listener to use?
3- What are the differences between TV and radio?
4- What preparation does a radio presenter do before he does an interview?
5- What is the advantage of mystery and spontaneity?
6- Does the presenter have to be at the center of the program?
7- How do you get intimacy in your documentary?
8- What has caught them by surprise ?
9- What effect does music have ?
10- What do they recommend?