A study is under way in Yosemite National Forest to determine the adult height of American pine trees. Specifically, the study is attempting to determine what factors aid a tree in reaching heights greater than 60 feet tall. It is estimated that the forest contains 25,000 adult American pines. The study involves collecting heights from 250 randomly selected adult American pine trees and analyzing the results. Identify the variable of interest in the study. a. The age of an American pine tree in Yosemite National Forest. b. The height of an American pine tree in Yosemite National Forest. c. The number of American pine trees in Yosemite National Forest. d. The species of trees in Yosemite National Forest