Base your answers to questions 48 through 50 on the rock columns below and on your knowledge of Earth
science. The rock columns represent four widely separated locations, W, X, Y, and Z. Numbers 1, 2, 3, and 4
represent fossils. The rock layers have not been overturned.
Which numbered fossil best represents an index fossil?
(1) 1
(2) 2
(3) 3
(4) 4