Dennis Is 45 Years Old and Both He and His

Dennis is 45 years old and both he and his 25-year-old wife are looking forward to being parents for the first time. They are aware of the risks associated with the parents' age and the development of schizophrenia. They recently read the results of a study by Dolores Malaspina and her colleagues (2001) , which showed that:

A) three-quarters of the cases of schizophrenia in the study were associated with older maternal age.
B) three-quarters of the cases of schizophrenia in the study were associated with older paternal age.
C) only one-quarter of the schizophrenia cases in the study were associated with maternal age.
D) three-quarters of the cases of schizophrenia in the study were not associated with older paternal age.