Question

read the passage.
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.
fevers are useful because they increase the bodys lymphocytes.
the hypothalamus responds to infections by raising the bodys temperature.

Explanation:

The passage discusses how fevers are a sign of the body's attempt to heal. It mentions that the hypothalamus responds to infection by increasing body - temperature, which helps prevent virus and bacteria multiplication and may increase lymphocytes. Fevers also serve as warning signs. The overall idea is that fevers help the body fight infections.

Answer:

Fevers are useful because they help the body fight infections.