John approaches problems systematically, considering various solutions and the consequences of each before he decides on the implementation of any one solution. john is probably at which level of cognitive development?

John is at the level of formal operations in terms of cognitive development. It is because this level, the formal operational, it is where a person has develop skills in terms of logical thought, reasoning, planning and in terms of having to have abstract concepts. It could be seen from his behavior as he demonstrated reasoning and logical though in approaching problems.

explanation:

allergens: overstimulate the nerve system

neurotics: attack nerve cells

mutagens: damage or otherwise alter dna sequence

generators: cause defects during growth and development  

carcinogens: cause unchecked cell growth

i hope you get the idea according to me these are the effects that happened.