How are models used

A. to predict an event
B. to describe a relationship that is difficult to see
C. to represent and abstract ideas
D. all of these

D

Explanation:

The purpose of models in ecotoxicology is the understanding, simulation and prediction of effects caused by toxicants in the environment. Most current models describe effects on one of many different levels of biological organization

satellites are frequently used to make observations of the orbit on earth

well, i believe that the answer is 2. : 3