Answer: Biological
Step-by-step explanation:
Biological causes of depression could be described as biological or chemical substances that could affect the hormones or brain of individuals which could lead to depression. This could be accessible through inhaling of chemicals in toxic manufacturing environment. Many people who works in some of this environment are affected psychologically which now reflects on their behaviour, some are usually aware of this and some aren't, some who are aware change jobs with time. It could be described that this is what Calvin is going through.