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

Explanation:

The passage details how fevers help in preventing pathogen - multiplication and increasing lymphocytes, indicating their role in fighting infections.

Answer:

Fever are useful because they help the body fight infections.