You’re correct in my opinion they all seem to be contamination
i'm unsure of your statement, but i believe that the statement is false. A rake would add more physical activity, since you're using both leg muscles while walking, and arm muscles.
Answer:
The relationship between stress and illness is complex. The susceptibility to stress varies from person to person. Among the factors that influenced the susceptibility to stress are genetic vulnerability, coping style, type of personality and social support. Not all stress has negative effect. Studies have shown that short-term stress boosted the immune system, but chronic stress has a significant effect on the immune system that ultimately manifest an illness.