Scientists analyzing trapped gases in ice cores drilled in Antarctica's ice sheets were able conclude that during the last 800,000 years when carbon dioxide concentrations in the atmosphere increased, the average global air temperature increased or decrease
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The primarily goals of the zapatistas of mexico in 1994 were land reform and redistribution. it is also included in their demands to have a greater political and cultural autonomy for the indigenous people of chiapas and the rest of mexico.

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.

Check -it can you examine advantages and drawbacks to possible solutions.check-it can you consider options to solve a problem.check-it can you persuade an audience to support a proposal.check-it can you identify the cause of a problem.

The correct answer is:   [b]:   "physical systems" .