Which of the Following Methods Would Most Accurately Measure the Density

Which of the following methods would most accurately measure the density of the population being studied?

A) counting the number of prairie dog burrows per hectare
B) counting the number of times a 1-km transect is intersected by tracks of red squirrels after a snowfall
C) counting the number of coyote droppings per hectare
D) counting the number of moss plants in 1-m2 quadrats
E) counting the number of zebras from airplane observations.