In which of these issues would the concept of nation-state be most important? A. air pollution
B. border security
C. job outsourcing
D. spread of epidemic diseases

Idon't know. the question you are trying to ask doesn't make sense.

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.

Answerstratovolcanoes///near or in the ring of fire;

Idk bro sorry  lava is hotter then magma but im  not sure about it alll