I think this would be the Great Wall of China!
although it's actually thought to be much, much longer: over 5000 miles long, if yoiu include natural defensive barriers used in it.
Land forms can affect people by elevation, like a plateau, it's elevated an means colder, which means less species, which means humans lving there adapt, something like that.
The correct answer is D, winds that blow inland from oceans or large lakes contain a lot of water vapor that will cause precipitation.
