What can cause attention deficit hyperactivity disorder (adhd)?

The exact cause of ADHD is not well known, however, some of the factors, which can lead to the condition. These are as follows:  

1. Genetic factors, as ADHD seems to run in families.  

2. Chemical imbalance taking place in the brain.  

3. Infections, poor nutrition, smoking, substance abuse at the time of pregnancy, and drinking.  

4. The toxins like lead can influence the development of the brain of a child.  

5. A brain disorder or brain injury, that is, destruction to the frontal part of the brain can result in the issues associated with ADHD.  

i think   the answer is c hope i'm right

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8