The Nurse Is Assessing the Knowledge of New Parents with a Child

The nurse is assessing the knowledge of new parents with a child born with maple syrup urine disease (MSUD) .This is an autosomal recessive inherited disorder,which means that:

A) Both genes of a pair must be abnormal for the disorder to be expressed.
B) Only one copy of the abnormal gene is required for the disorder to be expressed.
C) The disorder occurs in males and heterozygous females.
D) The disorder is carried on the X chromosome.