Final answer:
The geography of Atlantic South America is characterized by lengthy coastlines along the Atlantic Ocean, which have facilitated migrations and provide access to marine resources.
Step-by-step explanation:
The phrase that best completes the diagram describing the geography of Atlantic South America is Lengthy coastlines
Atlantic South America is characterized by its extensive coastlines along the Atlantic Ocean. The Andes Mountains, which run parallel to the coast, form a narrow coastal passage. This geographical feature has facilitated early migrations and transportation along the continent. The coastlines also provide access to important marine resources and support various economic activities such as fishing and tourism.
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