A) Correct answer. Genetic factors and chromosomal abnormalities are among the primary causes of congenital heart diseases. These conditions often arise due to errors in heart development during fetal growth.

B) This option is incorrect. While certain environmental factors may increase the risk of congenital heart diseases, they are not the leading cause of these conditions.

C) This option is incorrect. Unhealthy lifestyle choices, such as smoking and alcohol consumption, may contribute to heart diseases in adults, but they are not the primary cause of congenital heart diseases.

D) This option is incorrect. Vaccination is important for preventing certain infections, but it is not directly related to the cause or prevention of congenital heart diseases.