Answer
a) Please see the image.
b) The rapid rise of resistance could be due to use of insufficient DDT, which could be overcome by many resistant individuals, plus the fact that mosquitoes would have been subject to selection for resistance for all of those months. Resistant individuals could continue to reproduce.
c) Resistance could have spread rapidly both due to the widespread use of the selective agent (DDT), causing resistance to to become more frequent in many places (convergently) as well as the movement of resistant mosquitoes around the world.
Work Step by Step
This question asks you to put together real-world data with ideas about selection and convergence. Review those, and remember that selection can act in many places at once. Also recall how quickly mosquitoes breed, meaning that many generations would face selection in one year, leading to a quick rise in resistant populations.
