Scientists are required to to determine a substance’s risk. a. research how chemicals react with living cells b. conduct experiments to identify the hazard c. collect and analyze risk characterization data d. test effects on exposed populations e. all of the above

The answer is all the above.

A scientist is someonewho frequently engages in an activity in order to acquire knowledge using a scientific method.
If the scientist is studing the risk of the substance, he needs to acquire the most information as possible, so he:
conducts experiments to identify the hazard,
collects and analyzes risk characterization data,
researches how chemicals react with living cells and
tests the effects of the substance on the populations.