I teach in the rarified world of EAP, so it's a very long time since I've done this sort of thing. However, it looks to me, given the title, that they're looking for a simple description using the passive to describe the steps in a process, where the process is the focus. As it's inventions, just get something that proceeded in steps, like TV, starting with the rapid photography of Edward Muybridge, through Marconi and Filo Farnsworth. youshoudl be able to dig out some pictures or drawing for this, then the students can use these as prompts for language containing a lot of natural passives.
