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.

On September 13,1956, IBM shipped the first unit of the RAMAC, in other words, Random Access Method of Accounting and Control. The RAMAC, designed in Big Blue’s San Jose, Calif., research center would have made a lousy music player. The drive weighed a full ton, and to lease it you’d pay about ＄250,000 a year in today’s dollars. Since it required a separate air compressor to protect the two moving "heads" that read and wrote information, it was noisy. The total amount of information stored in its 50 spinning iron-oxide-coated disks-- each of them a pizza-size 24 inches -- was 5 megabytes.