If a city raises taxes, especially by an exponential amount, they risk people leaving the city to avoid them. If the city is struggling as is, meaning many of its citizens are poor, it would be virtually impossible to raise taxes without people leaving the city.
This could also increase the crime rate (people stealing things because they cannot afford them) and at times, new taxes are also difficult to put in place. However, these are unlikely to occur. Choice D is the best answer.