How has burning fossil fuels most caused a decline to the quality of air that people breathe? OPTIONS:
- by adding particle pollution
- by creating a hole in the ozone layer
- by causing acid precipitation to fall
- by increasing the levels of carbon dioxide
A: by adding particle pollution

A baby horse will inherit all of these traits from its parents except OPTIONS:
- height.
- weight.
- coat color.
- preferred food.
A: preferred food.

Many states require vehicles to be examined and to meet safety and pollution standards. What impact might vehicle inspections have on the environment? OPTIONS:
- The environment will not be polluted.
- The environment will become more polluted.
- Fewer pollutants will be released by vehicles.
- Fewer pollutants will be produced by older vehicles.
A: Fewer pollutants will be released by vehicles.

A species of bird has not been seen since the 1900s and is considered extinct. Which evidence would best disprove the claim that the bird is extinct? OPTIONS:
- A bird watcher makes a sketch of the bird.
- A scientist discovers fossil remains of the bird.
- A researcher takes a photograph of the bird.
- A park ranger finds a suitable habitat for the bird.
A:
A researcher takes a photograph of the bird.