A reorganização ocorrida após o fim da guerra fria deu origem a organizações econômicas em diferentes regiões do planeta, também chamadas blocos regionais. Os quais visam A) Os países estão dispersos cuidando de suas economias, não estabelecem relação.
B) O conjunto dos países que participam da organização mundial visam apenas a integração social.
C) Os países se reúnem para estabelecer relações de comércio privilegiadas entre si. Todas as iniciativas de integração econômica e monetária visam facilitar e ampliar o comércio entre os membros e reduzir custos de produção e de transportes, gerando maiores lucros.
D) Todos os países membros não estão interessados em reduzir o custo da produção, o que dificulta a integração.

Mantle convection is the process that drives plate tectonics. the theory of plate tectonics states that the crust is divided into plates that float on the semi molten mantle below. the circular motion of the magma as it slowly rises and falls or move though convection cells drags the plates along causing them to move. the heat source in the lamp would represent the earth's core. the core is the source of energy that drives convection in the mantle. the lava represents molten magma under the earth's surface. if the lava lamp had floating pieces they would move as the circular motion of the lava in the lamp as it rises and falls would move them along the surface. these floating pieces would represent pieces of the earth's crust. 

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.