The number of tornadoes recorded annually in North America has more than tripled since 1953. Yet meteorologists insist that the climatic factors affecting the creation of tornadoes are unchanged. Which one of the following, if true, most helps to resolve the apparent discrepancy described above? ['Many more citizens are helping authorities detect tornadoes now than in 1953.', 'The number of tornadoes recorded annually has increased only slightly in the last five years.', 'The factors affecting the creation of tornadoes were not well known to meteorologists before 1953.', 'The amount of property damage done by tornadoes has grown substantially since 1953.']