Which river valley civilization was conquered over and over again because it lacked natural barriers?

I’m his published 95 theses,martin luther protested against? a-the selling of indulgences within the catholic church b-the belief in predestination c-the worshipping of statues of saints d- the catholic church focus on faith as the sole means of salvation

Why is immigration so important today?

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