You have conducted an Ames test on a given compound. Which of the following would be classified as a positive result on the Ames test?

A) his+ strain grows on an his+ plate.
B) his- strain grows on an his+ plate.
C) his- strain grows on an his- plate.
D) his+ strain grows on an his- plate.
E) his+ strain grows on either an his- or an his+ plate.