People who hear a ringing or buzzing sound with no external source probably have _____

Ellen has PKU. Her husband does not have PKU but genetic testing has revealed that he is a carrier for the condition. The odds that their first child will have PKU are:

a. 0% b. 25% c. 50% d. 100%

Approximately 5% of the world's population has either attention deficit disorder or the related condition of:

a) attention deficit hyperactivity disorder. b) autistic disorder. c) Rett's disorder. d) Asperger's disorder.