According to the theory of continental drift, in prehistoric times, many of today' s separate continents were part of a single huge landmass. As the plates on which this landmass rested began to move, the mass broke apart, and ocean water filled the newly created chasms. It is hypothesized, for example, that South America was once joined on its east coast with what is now the west coast of Africa. Which one of the following discoveries, if it were made, would most support the above hypothesis about South America and Africa? ['Some of the oldest tribes of people living in eastern South America speak languages linguistically similar to various languages spoken by certain western African peoples.', 'A large band of ancient rock of a rare type along the east coast of South America is of the same type as a band on the west coast of Africa.', 'The climates of western Africa and of the east coast of South America resemble each other.', 'Several species of plants found in western Africa closely resemble plants growing in South America.']