Which of the following is true about the immunity to HIV?

About 10 percent of Europe’s present-day population seems to be resistant to HIV -- a significantly higher proportion than on other continents. Researchers have traced this immunity to a genetic mutation that seems to have appeared some 2,500 years ago, and that protects white blood cells against penetration by HIV. From the mid-14th century through the 17th century the prevalence of the mutation increased, in tandem with repeated outbreaks of the plague. The researchers suggest that the mutation protected against the disease, which culled the population of people who lacked it.

A study done in Greece says people can live longer and healthier lives if they eat what is known as the Mediterranean diet. Such a diet generally gets about 40 percent of its calories from olive oil and other fats that are considered healthy. Researchers from the University of Athens and Harvard University Medical School in Boston, Massachusetts did the study. They published the results in the New England Journal of Medicine. Researchers say it is all the foods together in the Mediterranean diet that make the difference. So they say people should eat a lot of fruits, vegetables, beans and fish. And they should use olive oil in their cooking.