Question

What is the link between heredity and the causes of mental disorders?

Answer 1

A. A person can inherit a tendency toward a mental disorder. 
In terms of heredity, this would be the best answer. Because heredity refers to biological factors, inherited through genetics of parents and relatives. Not always will that person develop a mental disorder due to a biological relative being diagnosed with a mental disorder, but it is possible and a high risk factor. The death of a loved one, using drugs or alcohol, and being neglected during childhood are more of environmental and psychological factors. 
Hope that helps. :)