A tourist attraction provides a guide for every group of 15 visitors. One Saturday, the owner uses the equation 15 × 8 = 120 to find the number of visitors that received a guided tour. What does the 8 in the equation represent?
the number of visitors that received a guided tour that day
the number of visitors in each guided tour
the number of groups that received a guided tour that day
the number of groups that received a tour over 8 days