In Widom's research on the relationship between early child abuse and later delinquency or adult ...

In Widom's research on the relationship between early child abuse and later delinquency or adult criminal behavior which of the following were considered to be either validity or reliability problems?
 
  a. using public school records and birth records from local hospitals to select the sample
  b. by using law enforcement data to assess delinquent and criminal behavior, Windom only identified those who were caught for their behavior not those who were criminally active but were not caught
  c. by using court data to identify those for the sample who were abused, Windom only knew about those cases where abuse came to the attention of the public officials, not all the cases that go unreported
  d. all of the above