The correct answer is B. The Louisiana Purchase.
Step-by-step explanation
The Louisiana Purchase is one of the most famous negotiations in history in which this region of North America comprising the territories of current states such as Arkansas, Colorado, North and South Dakota, Missouri, Iowa, Kansas, Louisiana, Minnesota, Montana, Nebraska, New Mexico, Oklahoma, Texas, and Wyoming (red zone in the map) were sold to the United States by France who had it under their control since the seventeenth century. This negotiation was between 1801 and 1803, when President Jefferson began negotiations with the government of Paris, with the then first consult, Napoleon Bonaparte for the purchase of Louisiana. This transaction was the first major step of the United States in its westward expansion. So, the correct answer is B. The Louisiana Purchase.