All of the following are examples of expansion diffusion, EXCEPT
the percentage of European Union coins circulating in France from other EU countries.
the organization of a company's top executives by world regions where the company sells the most of its product
innovative smart phone technology developed by one company being used by a competitor company
the rapid adoption in the United States of AIDS prevention methods.
teens in rural areas listening to hip hop music.

This is all you, but i can give you some topics that you could try. if it rained when you want to do something outdoors, it 'limits' that human activity. maybe you want to do an experiment that goes throughout the whole year and you have to have above freezing the entire year. this 'limits' your activity. i thought of those just off of the top of my head. something that gets to me that might be getting to you is you are thinking too hard about what to do. think simply, and if it is too simple, then bump it up just a little bit.

I'm pretty sure it's c. extremely gradual but not 100% sure though.

The genetic material (mrna) code for proteins. so the nucleus is the part of the cell.

Conditions are more like living on  land  for creatures in the upper part of the intertidal, which is only covered with  water  at extreme high tide, so life is easier on land. conditions are more like living in the ocean for creatures in the lower part of the intertidal which is only exposed to air at extreme low tide. so basically it both worlds of land and ocean.