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 recent report finds that the number of working hours in Asia has started to decline. But the economists say that what is needed is not only a reduction in working time, but also more flexibility in working hours. Both businesses and workers would profit if working hours can be adjusted according to demand, allowing workers to better control their days. And, as many economies in the region see a growth in service industries, such as hotels and restaurants, which need flexible work schedules, more flexibility could help boost growth.