The Victoria Falls is associated with the Zambezi River, making option 4 the correct answer. The waterfall is located on the border of Zambia and Zimbabwe in southern Africa, and is formed as the full width of the river plunges into a gorge. Let`s analyze the incorrect options as well for understanding:

Option 1, Amazon, is incorrect as the Amazon River is located in South America, not Africa, and does not have a connection to the Victoria Falls.

Option 2, Missouri, is incorrect as the Missouri River is located in North America, making it geographically far removed from the Victoria Falls in Africa.

Option 3, St Lawrence, is also incorrect because the St. Lawrence River is located in North America. This river is associated with several smaller waterfalls, but not the Victoria Falls.

In essence, the Victoria Falls is associated with the Zambezi River, not the Amazon, Missouri, or St Lawrence rivers.