The Abdominal Segments of Drosophila Have No Appendages

The abdominal segments of Drosophila have no appendages. Loss of function of bithorax genes results in appendages forming in these abdominal segments. Therefore,_________ .

A) bithorax normally activates a gene that negatively regulates appendages in the abdomen
B) bithorax mutations are necessarily recessive
C) ultrabithorax usually acts to oppose bithorax genes
D) bithorax genes normally activate appendage- forming genes
E) expression of bithorax wild- type genes suppresses all appendage formation