Final answer:
Tornado Alley consists of the central United States states that experience frequent tornadoes, specifically Texas, Oklahoma, Kansas, Nebraska, and South Dakota.
Step-by-step explanation:
The geographical region known as Tornado Alley typically includes several states in the central United States that are prone to frequent tornadoes. Based on the options presented, the correct answer would be:
a. Texas-Oklahoma-Kansas-Nebraska-South Dakota.
This definition of Tornado Alley reflects its most active part, stretching between the Rocky Mountains and the Appalachian Mountains. Storm chasers, whether they are amateurs, researchers, or media weather watchers, often frequent this region due to its high incidence of tornadoes.