During the 1980s and 1990s, the annual number of people who visited the Sordellian Mountains increased continually, and many new ski resorts were built. Over the same period, however, the number of visitors to ski resorts who were caught in avalanches decreased, even though there was no reduction in the annual number of avalanches in the Sordellian Mountains.

Which of the following, if true in the Sordellian Mountains during the 1980s and 1990s, most helps to explain the decrease?

【选项】The average length of stay for people visiting the Sordellian Mountains increased slightly.