European Rabbits Were Introduced to Australia in 1859

European rabbits were introduced to Australia in 1859. The rabbits reproduced rapidly in their new habitat, displaced other animals, and overgrazed vegetation. In an attempt to reduce the rabbit population, a virus was introduced in 1951. This virus is usually deadly to European rabbits.When the virus was first introduced, the rabbits died in large numbers, but the death rate decreased over time. Which of the following best explains the decrease in the rabbit death rate?

A) Young rabbits learned to avoid being infected with this virus.
B) Natural selection favored rabbits that are resistant to this virus.
C) The lifespan of this virus is too short to affect rabbits over a long period of time.
D) The rabbits that were originally infected with this virus have been dead for many years.