Sigma virus infection in Drosophila melanogaster causes flies to become paralyzed and then die in ...

Sigma virus infection in Drosophila melanogaster causes flies to become paralyzed and then die in high concentrations of CO2. The virus is passed on extrachromosomally.
 
  Two isogenic strains of Drosophila cultures are maintained: R (resistant to CO2 or wild type) and S (susceptible to CO2, infected with sigma). After crosses between male R and female S flies, subsets of offspring of each gender are tested for CO2 sensitivity. Which of the following results do you expect? A) All the offspring are sensitive.
  B) All the offspring are female.
  C) All the offspring are male.
  D) All the offspring are sensitive, but only males pass it on.
  E) Only male offspring backcrossed to the female parent are sensitive.