A Child Recently Has Been Diagnosed with Leukemia

A child recently has been diagnosed with leukemia.The child's sibling is expressing feelings of anger and guilt.This reaction by the sibling is:

A) Abnormal,and she should be referred to a psychologist.
B) Unusual,as the illness doesn't affect the sibling.
C) Unexpected,as the cancer is easily treated.
D) Normal,as the sibling is affected too,and anger and guilt are expected feelings.