Which of the following best describes a "sedative"?

A sedative is best described as tending to soothe or tranquilize. This term is commonly used in the context of medicine, where sedatives are substances that promote calmness, relaxation, or sleep. They are often prescribed to help individuals manage anxiety, stress, or sleep disorders by exerting a calming effect on the central nervous system. The essence of a sedative lies in its ability to decrease activity and induce a state of tranquility, making option C the most accurate description.

In contrast, the other options do not accurately reflect the nature of a sedative. Increasing energy suggests a stimulating effect, which is the opposite of what a sedative does. A method of public speaking is unrelated to drug effects or calming actions. Similarly, a type of physical exercise involves activity and exertion, which is contrary to the soothing and tranquilizing effects of sedatives. Therefore, C is the most suitable choice in this context.