Fact 1: The emission of sulfur dioxide causes acid rain.

Fact 2: Acid rain effects forest ecosystems.

Given the two facts above, answer the question "What causes damage to forest ecosystems?" with the following options: 
- flooding
 - humans disturb it
 - Sulfur dioxide
 - deforestation
 - Liquid bromine
 - Carnivore animals
 - Pollution
 - Hydrogen peroxide


 

   Sulfur dioxide      