A 30-mi. stretch of highway has markers every 0.2 mi. The first marker is at the 0.2 mi. mark and the last marker is at the end of the highway at the 30 mi. mark. If n is the number of markers, which equation is true?
A. 30 • 0.2 = n
B. 30 • 0.5 = n
C. 30 • n = 0.2
D. 30 ÷ 0.2 = n