An ecologist suspects that an otherwise healthy forest ecosystem experienced an unusually high level of acid deposition during a snowy winter. Which of the following should the ecologist measure to help confirm her hypothesis? I. the numbers of malnourished and/or poisoned trees
II. the aluminum concentration in the soil
III. the pH of the snowmelt
a. I only
b. II only
c. I and II only
d. II and III only
e. I, II, and III