Question

Which of the following would demonstrate that the fruitless (fru) gene is necessary for male mating behavior in flies?

a) mutation of the mouse fru homolog results in changes in mating behavior in mice

b) ectopic expression of fru in female flies causes them to exhibit male mating behavior

c) fru was cloned and shown to encode a transcription factor

d) loss-of-function mutations in the fru gene cause abnormal or absent male mating behavior

Any help would be appreciated, but I would prefer a detailed response over just stating which is right.