Scientists use computer models to study complicated events and to a. perform experiments
b. state theories
c. change theories and laws
d. make predictions

The correct answer is - d. make predictions.

Explanation:

Computer models are scientific models that help in analyzing complex systems. Scientists use these to analyze data and on the basis of these data computer models are able to predict the outcome of the problem or can tell what will happen in the future.

These are very helpful in complex systems and are made on the basis of the data collected and are the basis of the models. Weather forecast can be predicted on the provided data.