Correct answer: C. the western coasts of Europe and Africa
According to the continental drift theory, which was taken most seriously first by Alfred Wegner, although there were some mentions to its possibility before, the Americas, North and South, have formed next to Europe and Asia, as well as Africa, respectively, a single continent. The eastern coast of North America would have been in contact with the western coasts of Europe and Africa (mostly at north), therefore, if you found a mountain chain on the eastern coast of North America, you would probably find its continuation on the western coasts of Europe and Africa.