Which statement describes how doctors use their knowledge of genetics in medicine?
dna analysis is used in the study of inheritance and disease.
genetic testing can diagnose disease.
genetic engineering may some day be able to prevent disease.
all of the above

All three objects are quite possible, so the Answer is all of the above.

Certain diseases can have hereditary dispositions; such as Diabetes Mellitus Type II or Hypertension. Genetic engineering of diseases can go so far as to have viruses that are programmed to fight certain diseases, or to cure cancers. 

Maybe meditation,stress relievers,try to have quite time try to get school done on time and try to go to bed earlier