Is it possible that the human skeleton and the chalk with which this person writes on the blackboard contain the same chemical element calcium?
Calcium is a macronutrient – it is found in living organisms in significant quantities. The chalk is formed by representatives of the animal kingdom (mainly the shells of unicellular organisms). The shells contained calcium.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.