The graph shows the rabbit population in South Australia over time. It also shows the measures that were used to control the size of the population and prevent the population from increasing too much. European rabbits were introduced into Australia in the 18th century and are considered an invasive species. Without the normal environmental limiting factors, the rabbit population grew exponentially with a higher carrying capacity than other native mammals.

Through the 20th century, humans have used diseases or parasites to reduce the rabbit population in Australia. Myxomatosis and rabbit hemmorrhagic disease (RDH) are both diseases that kill rabbits. Rabbit fleas are a parasite that feeds off of the rabbits blood, causing the rabbits to be sick and not healthy enough to reproduce. This graph shows the effects of all three methods on the rabbit population.

Which of the diseases or parasites had the greatest effect on the rabbit population?

a
All methods were equally as effective at reducing the number of rabbits in the population
b
The introduction of RHD had the greatest effect on the rabbit population, and afterwards, the rabbit population did not fully recover.
c
The introduction of rabbit fleas had the greatest effect on the rabbit population, and afterwards, the rabbit population experienced exponential growth
d
The introduction of myxomatosis had the greatest effect on the rabbit population, and afterwards, the rabbit population did not fully recover.