<span>B. Combat troops in trenches
Have a lovely day ;)</span>
Basically, Europeans would go to Africa and either enslave the locals by fighting or buy them from local warlords who were locals. They would then take the slaves to their new colonies where they would work until they die or they get sold, like sugar plantations or similar things.
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In general, this is correct, although the phrase has more to do with the
idea that people use religion to "lower themselves down" in everyday
life. It doesn't necessarily refer to rewards in an afterlife.
The Eastern Roman Empire capital of Byzantium received a name change when it's famous emperor Constantin died. For that reason its name was changed to Constantinople. This name stayed with Constantinople for a very long time.