Which fact supports the following conclusion? Explorers are responsible for introducing livestock to North America. Cortez introduced cows and sheep to Mexico. During Columbus's second voyage, he brought cattle to South America. De Soto brought his excellent cooking skills to Florida. Columbus introduced maize and potatoes to the European economy.

The correct answer is - Cortez introduced cows and sheep to Mexico.

The explorers and the settlers that came after them were responsible for lot of things, one of which was the introduction of livestock to North America. Cortez, along side his army, brought multiple domesticated animals in Mexico. The reason for that was that they needed them as food source. Since they actually stayed in the newly conquered territories, the animals stayed as well, multiplied, and they were spread around the continent.

Since Mexico is part of the North American continent, the introduction of cows and sheep in Mexico can be seen as the initial introduction of livestock in North America.