A scientist is designing an investigation to study the impact of predatory trout on the population of the mountain yellow-legged frog in a recreational nature park. What is most likely the test variable (independent variable) for the study?

James hutton is ? a. extensively studied fossils. b. revealed that fossils would provide the history of past life. c. created the first scientific classification of plants and animals. d. provided geologic evidence necessary for calculating the time span of evolution.