I believe it's A. If the birth rate and immigration is equal to the death rate and emigration, then they balance each other out. If birth rate and immigration is bringing people in and death rate and emigration is pushing people out, then they equal 0.
During the latest ice age on Earth, huge, frozen glaciers of snow and ice slowly crept along the surface of the planet. These glaciers crushed and flattened many solid, rocky features on the land. This is an example of the _______ interacting with the _______. A. cryosphere; geosphere
Air. If you read reports from the past decade, you will find that the air quality in china is so poor that people have to put a mask on just to walk outside.
I think that the key point here is the "easily reproducible" - because all of them can be scientific questions (even a! it could tell us about about the human psyche!)
but d. is the best answer for a reproducible experiment. B could also make a good experiment, but it would be too expensive to be easily reproducible. C is calling for a more complex analysis that is too complex for an experiment. And a would require more questionnaires than experiments
