By age illness and disease overtake accidents as the leading cause of death, and, statistically speaking, this is the first time this occurs since infancy.

35                

Explanation:

          Senescence is a biological process or condition of deterioration of the human body with age. The average age considered for the biological senescence for human beings is 35 to 40 years.  

           From senescence to human being, diseases and illness are the main factors for the death of a human being because as a person ages their physiological structure and function changes. They become weak and is more prone to diseases. Thus they are more likely to die from diseases than from meting with an accidents. Because person ages, they become more mature and their cognitive traits help them to take more mature and responsible steps in life.

           But in childhood or since infancy, an individuals cognitive traits are not properly developed to take matured decisions. So the death of many teenagers are caused by accidents.

Therefore the answer is -- 35

[content deleted] - user123802726recklesschicken

i am not in high school so i don’t know