Answer:
Confounding variable
Explanation:
Confounding variable refers to the type of variable that can disrupt the validity of the experiment by giving a certain effect to the variable.
The experiment above was designed to measure mood elevation among the subjects, but the living situation among the subjects are really different among one another and cannot be controlled by the researchers.
This is just an example of how people in late adulthood continue to be <u>productive </u>in many ways.
<h3>Productive</h3>
When someone is productive it means that the person is hard working and engages in different tasks.
Hence, Anna is productive because she was a volunteer worker before another job was introduced to her which was a senior community Centre.
Learn more about productive here:brainly.com/question/2992817
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D. Two federal courts and a local trial court, but no local court of appeals