A Child Has Recently Been Diagnosed with Leukemia

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

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