Erwin and Scott Used an Insecticidal Spray to Remove Insects

Erwin and Scott used an insecticidal spray to remove insects from the top section of an L. seemannii tree and collect them from the forest floor. Using the data collected, Erwin projected that this entire tree, from top to bottom, is host to about 600 unique arthropod species, which were not found on any other tree species. While the researchers also identified 900 beetle species from the top section, the vast majority of them were known to be found on many other tree species. If there are approximately 50,000 species of tropical trees, and assuming that every tree hosts a similar number of unique species, which of the following would be the best quantitative method to roughly estimate the total number of arthropod species, globally?

A) Estimate the species density and then multiply by 50,000.
B) Multiply 600 by 50,000.
C) Multiply 50,000 by 900.
D) Add 900 to 600, and then multiply by 50,000.