Read this excerpt from "A Student's Guide to Global Climate Change." Climate change might allow some infectious diseases to spread. As winter temperatures increase, ticks and mosquitoes that carry diseases can survive longer throughout the year and expand their ranges, putting more people at risk. One big concern is malaria, a deadly disease spread by mosquitoes in many hot, humid parts of the world. What can people do about it? People should take common-sense steps to avoid tick and mosquito bites, and communities can take actions to control mosquitoes, such as removing sources of standing water. It's also important for doctors to know the symptoms of diseases that could be spreading to new areas so they can diagnose and treat their patients. This excerpt uses what text structure?