Question

how fevers help
fevers can be uncomfortable, but the upside is that they are evidence of the bodys attempt to heal. when a person develops an infection, a section of the brain called the hypothalamus recognizes a threat. the hypothalamus responds by increasing the bodys temperature. since both viruses and bacteria are temperature sensitive, this environment helps prevent them from multiplying. in addition, scientists have found evidence that fevers may increase the number of certain lymphocytes—white blood cells that are part of the immune system. increased lymphocytes make the body more effective in destroying infected cells. of course, this doesnt mean that high fevers dont warrant medical treatment. in fact, another reason that fevers are beneficial is that they serve as warning signs, indicating that something is amiss.
what is the main, or central, idea of the passage?
fevers are useful because they help the body fight infections.
the hypothalamus responds to infections by raising the bodys temperature.
fevers are useful because they increase the bodys lymphocytes.

Explanation:

The passage starts by stating that fevers are evidence of the body's attempt to heal. It then explains how the hypothalamus raises the body - temperature in response to infection, which helps prevent virus and bacteria multiplication. It also mentions that fevers may increase lymphocytes, making the body more effective at destroying infected cells, and that fevers serve as warning signs. All these points support the idea that fevers help the body fight infections.

Answer:

Fevers are useful because they help the body fight infections.