C. A researcher can control the environment and observe the response.
Explanation:
A researcher is able to control in the environment since he may alter or manipulate the independent variable for example in a simulated environment. By altering the independent variable, the researcher may alter the environment for the experiment and therefore change the dependent variable in the experiment. He then observes to see the response of the dependent variable
working with other governments to oppose the regime calling for transition to democracy imposing sanctions recognizing opposition groups providing humanitarian aid
