Suppose you have just discovered a Drosophila gene that has a sequence similar to a gene of interest ...

Suppose you have just discovered a Drosophila gene that has a sequence similar to a gene of interest in humans. You need to have mutants of the Drosophila gene because __________.
 
  A) you need to see whether fly mutants have a defect in the same system
  B) you need to see whether the mutant produces the same phenotype
  C) you need to see whether the Drosophila mutant disrupts the same metabolic pathway
  D) you want to compare the mutant Drosophila sequence to each mutant human sequence
  E) you need to have as many alleles in Drosophila as you have found in humans