What geographic feature protected Rome from an invasion from the north

The Alps, located on the northern border of modern-day Italy, seal off the peninsula from the rest of Europe during winter. This natural roadblock protected Rome from outside invasions by forcing attackers to move slowly through narrow passes, giving the Romans time to respond.

no statements but ok.

the statement that best describes the idea of manifest destiny that was used in the 19th century would be that "it was fate that the united states would continue to  expand westward," since people thought the us was "destined" to do so. 

these civilizations were located around fertile rivers, where they could produce an abundance of crops