Which defines background extinction?
question 17 options:

an accelerated extinction rate

extinctions of unknown species

mass extinctions in the past

the natural extinction rate

"The natural extinction rate" defines the background extinction

Explanation:

The background extinction rate which is being used for the evaluation of the rate by which the extinction in the earth's geological as well as the biological past took place before the contribution of the human beings as the primary contributors to the extinctions. Extinction happens when the last species of the plants or the animals dies out. This occurs as a result of the climate change or human activity.Background extinction occurs at a steady rate over geological time and is the result of normal evolutionary processes, with only a limited number of species in an ecosystem being affected at any one time.

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added