The results of the treatment of 20 boys with SCID-X1 showed that ____.  

A) SCID-X1 can be cured through genetic engineering
B) none of those treated were cured of the disease
C) a bone marrow transplant can cure SCID-X1
D) our understanding of the human genome exceeds our ability to modify it
E) the "treatment" caused numerous unforeseen complications.