Answer:
pollution
Explanation:
The correct word would be pollution.
<em>Pollution can be described as the presence of ecologically harmful substances in the environment. </em>
Littering the ground is considered pollution because it is harmful to the environment in the long term. Harmful chemical in water is outrightly considered pollution because this will hurt the organisms living in the water and rendered the water unusable to those around it.
An experiment or survey must be controlled in order to receive accurate results.
In an experimental group, the independent variable is changed. But in the control group, the independent variable stays the same.
