I am a little confused how we are picking the necessary versus sufficient conditions for these examples. The lesson just says "choose one," but it always just seems like the correct one without explanation of why the other one would not work. I think I am confused because by just "picking one" it makes it seem like either clause could be the necessary condition so it doesn't matter. But that is not the case right?

For example in question 5 we established that:

Sufficient: recent tech. advance producing

Necessary: not applied to producing power at traditional plants.

why can't it be?

Sufficient: applied to producing power at traditional plants.

Necessary: not recent tech. advance producing

If anyone has some insight on this I would appreciate it.