What is the difference between main effect and a secondary effect

It will be through raising high the prestige of your administration by success in short-range recovery, that you will have the driving force to accomplish long-range reform. on the other hand, even wise and necessary reform may, in some respects, impede and complicate recovery. what is the purpose of the transitional phrase on the other hand in this excerpt? a) it provides a counter-argument to the writer's main ideas. b) it provides a hypothetical situation for the reader to ponder. c) it provides additional evidence in favor of the writer's argument. d) it provides information about laws that are opposed to the writer's argument.