An ecologist suspects that an otherwise healthy forest ecosystem experienced an unusually high level of acid deposition during a rainy spring, due to the emissions of nearby power plant. Which of the following should the ecologist measure to help confirm her hypothesis? (3 points)

The amount of sulfur trioxide released by the power plant

The composition and amount of seasonal rainwater

The daily production of sulfur dioxide from motor vehicles

The amount of sulfur trioxide in the air surrounding the forest