D. To research its historical background and original purpose
This gives you the information and reason behind the work and explains where it comes from
<span>Depression is linked to an imbalanced level in serotonin. Serotonin is a neurotransmitter that is produced in the brain. These neurotransmitters helps the brain to send and receive messages from one part of the body to another. Serotonin affects nearly all the cells within the brain. As a result human behavior, mood, sleep, and even appetite can be greatly influenced. Aggressive behavior although can result from the same imbalanced levels of serotonin. Researches believe that the lack of receptors, or the inability for serotonin to reach these receptors, may also impact our ability to control anger and aggression.</span>
Answer:
<u>"the independent variable—whether or not the students receive money for doing puzzles—has a significant effect, such that students in the paid group spend less time doing puzzles during their break time".</u>
Explanation:
<u>Independent variable:</u> In psychological research, the term "independent variable is described as a variable that is being manipulated, altered or changed by an investigator or researcher in order to see or notice its effect on the dependent variable of the given study. Thus, the independent variable has a direct impact on the dependent variable.
<u>In the question above, the research finds that "the independent variable—whether or not the students receive money for doing puzzles—has a significant effect".</u>
What activity’s do you mean.