Final answer:
About 75 percent of the world's tornadoes occur in the United States, mainly due to the unique geographical and meteorological conditions, especially in the region known as 'Tornado Alley'.
Step-by-step explanation:
The question asks about the percentage of tornadoes that occur in the United States in comparison to the worldwide count. The correct answer is (d) 75 percent. The United States experiences a disproportionately high number of tornado occurrences compared to other parts of the world.
Tornadoes are particularly common in the central part of the country, an area often called "Tornado Alley." This region is susceptible to tornadoes due to its unique geography and meteorological conditions. The figure of 75 percent represents the average percentage of tornadoes that occur in the United States versus the global total.