Question: Which other well-known river system shares an ancient history with the Amazon River?
Answer: [C] the Congo River
Summary: At one time the Amazon River flowed westward, not eastward as it does today. This may have taken place when the pre-Congo river system flowed through present-day Africa when the continents were formed in the supercontinent, Gondwana. Over 400 million years ago, Gondwana existed before it was broken up over time into the seven continents we know today. This separation is due to plate tectonics, a phenomenon that is still pushing continents together and pulling them apart. The Amazon River now flows from west to east with its headwaters in the Peruvian Andes.
Source: Monga Bay, Rhett Butler; http://rainforests.mongabay.com/amazon/