Fact 1: Planting trees has a positive impact on an ecosystem.

Fact 2: Birds are important components of ecosystems.

Given the two facts above, answer the question "What has a positive impact on birds" with the following options: 
- exercise
 - planting trees
 - recycling
 - community policing
 - food and shelter
 - with their fur
 - squirrels
 - four limbs


 

  planting trees       