All of the following are examples of physical boundaries except:
a. an ocean
b. a mountain range
c. a barbed wire fence
d. a rive

When geographers describe how two places are related to each other spatially, they are describing a. where the places are located in relation to one another b. what kinds of natural environments are around each place c. how each place is changing over time d. what kinds of cultures are in each place

Some gamma ray bursts are hypothesized to come from mergers of neutron stars or black holes. if this hypothesis is correct, what else should we in principle be able to detect from such mergers? a. gravitiational waves b. x-ray bursts c. significant disruption of gas thousands of light-years away in the surrounding galaxy d. an "afterglow" of bright visible light, lasting for weeks

Which country in the video has the highest population growth rate?