The Santa Catalina Mountains near Tucson, Arizona, Are Covered by

The Santa Catalina Mountains near Tucson, Arizona, are covered by

A) cacti near the base, and then grasslands higher up, and then gradually thicker stands of trees even higher.
B) cacti near the base and then scrub/scattered trees higher up, and then gradually thicker stands of trees even higher.
C) grasslands near the base and then cacti higher up, and then scrub/scattered trees even higher.
D) rain forests near the base, and then temperate forests higher up, and then boreal forests above the tree line.